Scaling SVG Graphics with Javascript (3)

Here I would like to summarize my experience and tips about scaling svg with JavaScript.

Change Only Red Marked Scripts

First, I have shown two ways to scale svg graphics. The first way is to add scripts to both html and svg files. Even the scripts are quite long, actually you need to do is just copy-and-paste scripts. As I explained in demo, the blue area of scripts are ones you do not need to make change. The only scripts are marked as red or marked by '!!!...'.

I tried to make the scripts as generic as possible so that you do not need to touch. The only scripts are variables you have to set. As in the first way to call functions from html to svg, you need to set the object tag id in html being consistent with a var in svg. This will enable the svg to attach functions to object element in html.

I would recommend you to set the var in svg first as unique as possible. For example, you can name the var as first 10 char of svg plus a time stamp as the var name like 'ClipArtDog200810281259'. If you do this, it most likely there will be no other svg in your htlm file have the same svg with this name. This may reduce your touch svg file. What you need is to verify svg's top g id name.

The second way to scale svg is done by using JavaScript only in svg file. Normally, you don't need to change the scripts. I have defined some 'constant' vars in the top part of JavaScript for the size of circle and colors for the scale down and up. You may change them at your preference. I'll add one more method to enable and disable in-svg-scaling-scripts. So you will have control from html or in svg to disable the behavior.

SVG Grphics

As you know, svg graphics are defined as in xml files. It offers great control for art designer and programmers to create vector graphics with animation effect and unlimited potentials.

I used the InkScape tool to create svg with scripts(actually vim for adding scripts). When you create svg files, you may see the scaling scripts not working well. There are many reasons that may cause the problem. You should examine the svg xml file by a text editor. One issue is the transform function or tag used in the top g tag. This is not necessary because you could place the graphics in the right position by setting other position and size tag attributes. If you find it, you can remove it and use InkScape to make proper adjustment, selection and save.

Another issue is that you should not try to use scripts to create graphics dynamically since some hard-coded size values may not be scaled. As you can see my small circle with size of 5 px as radium is small enough but they are not scaled. These circles are created by script for scaling UI.

Not Working for SVG on Different Sites

As I discussed in the past two blogs, if you place your svg on different sites other than the size where your html file is hosted, the JavaScripts will not work! This is JavaScript security issue. I think there is nothing we can do. Just image if you would refer to another site to execute JavaScript codes, that would open a door for hackers to pull valuable information about the client sites and you have not place to trace down.

JavaScript has is security concern for adding scripts on html file. The browser will not allow you to execute scripts on a mysterious site.

Therefore, in order to make it to work, you have to have the total control of your html file and svg file on one site.

I am so sorry that I could not show you the demo on my blog since I cannot place svg to my blog site.

That's great experience for me to explore svg and JavaScript. I may add some more features like mirror-flip and transform to svg. I'll blog those and update my demo on my blog. Enjoy programming!

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Scaling SVG Graphics with Javascript (2)

In the previous posting, I have provided a demo example how to add scripts to scale svg grphics. I was going to add svg graphics in my blog and to show the scaling feature. However, I struggled for two days to make it working but without luck.

I can add script functions to my blog through Blogger's layout settings. In this sense, I have control of my HTML page. Here I mean by having control of HTML page is that you can edit and update the HTML page to web sever. However, I cannot find a way to submit svg graphics to my Blogger server. What I tried was to upload my svg to another site, Open Clip Art Library. I added my scripts to a svg xml graphic.

This brings a problem: my Blogger and my svg are in two different sites. What I found out is that the scripts in my blog does not have access to the scripts in my svg file. JavaScript has security reason to prevent calling scripts on other sites. What have been working in my local computer as shown in the demo would not work any more when I changed the svg reference to a different site!

In order to make this working, you have to put svg in your site.

Anyway, the instructions in my demo still work well if you follow this rule: you have the control of both html and svg files on one site.

The demo shows you a way to attach script functions defined in svg to the object in your html file. In JavaScript world, anything is object. A tag <object> is a DOM element. It also can be obtained by DOM documention object's getElementById() method. The unique feature of JavaScript is that you can attach or detach a function as a method to a object dynamically! That's basic technique I used in the demo. In this way, you can control the scale of svg from your html page.

That is one way to do it. I further investigated an alternative way to scale svg: adding scripts to a svg xml file. This provides some UIs in the svg: two small circles on the top-left corner the svg graphic with some mouse events(mouseover, mouseout and mouseup for click). By clicking on the left circle, it will scale down the svg; while clicking on the right circle, scaling up the svg.

I thought there is no attachment from my html and svg. The scripts in svg should be able to work. Nop! Since the svg is referenced by another site, any function or DOM method calls stop working.

Here is my svg with scripts at Open Clip Art Library. I put it here but the scripts in the svg do not work:



Open the dog graphic in another tab or browser window. Try it out and enjoy it!

NOTE: don't zoom in or scale the svg too big. It will slow down your browser for minutes. I event got crash once! If you scale too small or too big, refresh the page to restore to its original size.

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Scaling SVG Graphics with Javascript (1)

This blog, as well as coming ones, contains information about how to scale svg graphics by using JavaScript. It is based on the article of svg scaling with JavaScript. You need to have the control of the source codes of both the html page and svg so that you can add JavaScripts codes.

I discovered svg just recently, and like it very much. Inread of using jpg or png like bitmap graphics, svg is totally based xml. It is a standard way to display graphics at much more control by programmers. However, the first problem I encountered is to scale svg, or change the size of svg graphics. Soon I found the above article. It provides a very simple way to scale svg. It has limitations. The biggest problem is that it can only scale one svg graphic since it linked the graphics set dimension and scale methods to top window object. There is only one top window object.

Then I spent some week's evening time to figure out alternative ways to do it. Finally, I got a better way to scale svg. You can scale as many svg graphics as you like and the scales for each one are different. I am very satisfied with the current solution. Here I put them summarized in this and coming blogs, as well as some examples.

Here is the link to get the demo of HTML and SVG graphics files.

Enjoy it.

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Stack OverFlow: Developers' Q&A Social Site

I found a very good web site: StackOverFlow. It is basically a developers' Q&A social group. You can post any questions there. All the questions are categorized by tags. I added some tags I am interested in and some questions. Actually, I posted some answers first.

I got this web site information while I was walking outside downtown Calgary during my lunch break, listening a podcast by Scott Hanselman. The topic is all about StackOverFlow web site for almost one hour. That's great talk.

Today I google the site, found it, and joined the site. One interesting thing is that you don't need to create a new account. I used my Blogger account(googl's actually) to join the site. That saves me time and brain for another new account. Just for a few hours, I earned 1 point for my reputation. It is an encouragement to spend sometime to share programming experience and learn something as well. I always get valuable knowledge and solutions from web, forums, and discussion groups. This one is the right one for me! I think I'll use it more than other ones. One shop for almost all my skill areas.

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SVG and DropBox Web Share Space Tool

SVG is a xml file for defining graphics and it is a World Wild Web Consortium (W3c) recommendation. It is very cool graphics. With SVG, it opens a door to create interactive and dynamics graphics with scripts so that web page content is more dynamic.

One interesting about SVG graphics is that you cannot copy the image by right click. The image is defined by xml source codes in a SVG tag. What you can do is to open the source codes and copy the SVG tag section and save it as a SVG file. You can either use a browser or Adobe SVG Viewer. There are many SVG editor tools available as well.

The graphics is defined as SVG tag in an xml file. However, one problem is that you cannot directly place the xml graphics section in a html web page. It has to be placed in the same way as other graphics, ie, referenced by a link. Therefore I could directly place a SVG graphics in my Blogger, when I first learned about SVG. Blogger does allow me to place a graphics like jpg or png files, but does not support SVG. Blogger does not provide any space for me to directly put my files.

Today, I found a web tool called as DropBox. It is a web tool to share your files between you computer and your account there. With DropBox public shared space available. I can place my svg files there so I can reference to it by using embed tag.

Here is one svg file I saved in my public space and make a short name to it:



medium

Or click Feather Pan. I got this SVG graphics from Open Clip Art Library by wsnaccad.

I created a short name by MetaMark for the long name link. The only problem is that both tools are only active if your file and link active at least something like 90 days. I am not sure how long they are available. Anyway, for a blog entry, as long as it is working for the time being, it is OK. I can change the link later on if they are not working. There always some other options available.

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Add Categories or Labels to My Blog

I have added Blogger's new gadget Labels to my blog. To add a gadget is very simple. Just go to your blogger's Layout tab in Customize link on the top right corner. There should a link as Add a Gadget in the layout page:


To add a label to your posts, just type a label text in Blogger's editor's lower right input box ("Labels for this post"). If you have already defined some labels for your posts, you may see some labels displayed as Label Sense Completion.



To remove a label, you have to remove that label from all your posts.

It is really nice to be able to display Categories in my blog so that I can easily jump to the posts I did before. In addition to that, I'll have a picture what I have posted. For other browsers, I think this provides valuable information about my blogs.

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JavaScript Class-less Objects

Nice article on JavaScript Class-less Objects. Enjoy reading the article!

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Blogger Layout and Gadget

I have not touched my layout for a long time. Today I tried to add a twitter to my blog my new twitter account. I realized that I can also add a twitter gadget from Blogger's layout. Actually, there a tons of gadgets available. That's really great! I like some of them.

One of gadgets is Label, something like tags you can define for your blog. While you create a new blog, you can add labels on your blog. This is a very convenient way to group blogs. With Label gadget, you will provide a way for you and other browsers or follows to get interested topics. I'll try to add my own labels to my blog. Hopefully, the Label gadget will be able to provide some visual information about those labels.

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Web Tool: Short URL

I read an article about web tool to make URL short long time ago (last year?). That is ShortURL. However, the site may not free soon as I recall a warning in the article. Now I think that I do need a tool to redirect long urls such as my blog entries to a short one. By gooling web, I found MetaMark.

The short URL generated by this site is not a user friendly one, but it works. According to the information of this site, if the url has not been used for more than two years, it may expire. For short term use, this web tool is great. For example, my previous post is at http://xrl.us/otgzf, comparing to http://davidchuprogramming.blogspot.com/2008/10/web-tools-firebug-and-smushit.html.

Here is the form I copied from the site to do the job:

Enter a long URL to make shorter

I did several tests. If you use it to generate one and try the same long URL again, the one first time generated is returned back. Therefore, you just cannot change it. It does not check if the URL exists or not. I gave a none-existing one, and it still generated a new short name, which is not not-found-url. May be this is a way to change it (by making the previous existing one invalid). The web server just generates an alternative short URL, no matter the URL you provide is valid or none-short one. I tried to get a short URL for "http://google.ca". The new one is "http://xrl.us/bemw2" (it may exist or I just generate one for it):).

A related technique about URL is to implement ASP.Net's MVC framework. Its URL is based on controller, action and router. You can construct your own user-friendly URLs. The URLs based on ASP.Net MVC does not contain .aspx or .html suffix and not url parameters like ¶1=value1... You will see more short and user friendly URLs on web. The Metamark page mentioned that it is using MVC pattern. Maybe this server just use the pattern to build a very simple, random and short URL mapped to a long URL.

You can do the same thing for your company's web pages. Most of them are not-user-friendly URLs and hard to remember. By using ASP.Net and MVC framework, you can define a structure of URL and mapping user-friendly URLs to a existing ones without any change to the old ones. It should be very simple project.

Update: One of the great feature of Metamark web tool server is that you can provide a nickname and secret. The nickname must be unique one, not taken by others. Then the generated URL is [server_home]\[nickname]-[secret]. You could create a user-friendly URL! This blog is at http://xrl.us/shortURL1-WebTool. "shortURL" has been taken. I had to add "1" to it.

The generated short URL does not take any suffix like ".aspx" or ".html", which is not needed actually!

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Web Tools: FireBug and Smushit

Two great tools for Web developers: FireBug and Smush.it.

FireBug provides a view panel on the bottom with a lots of options to view such as Console, HTML, CSS, Script, DOM and more. If you click on Inspect to toggle it on, then you can hover your web page to see selections with updates on FireBug panel. I think it will save a lots of time for Web-developers to debug their web-pages. You may find out more about what actually in your client side web page codes when you debug your ASP.Net applications.

Smush.it is a great tool by some Google developers. You simply upload your image and to see how much it can smush. For example, I posted a blog on my Mac log with png image. After smush.it, it reduces 37%. The logic is very simple. It tries to turn off some image bits which will not make much difference in view. I'll use this tool to reduce my images on web. It for-sure will make your web page much faster for your clients!

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Apple Programming: User Defaults

Just started to look at some Apple Xcode application examples. That's a whole new huge framework for OS X. One application is about user defaults. In Windows there are many ways to store application defaults or values such as Registry, XML file, Ini file or Active Directory.

In Mac OS X, Apple provides a plist and bundle for user preferences and in Objective-C, there are some classes can be used to get user default values, NSUserDefaults for example:

NSUserDefaults *defaults;
// Get all the defautls for the current app
defaults = [NSUserDefaults standardUserDefaults];
// Register 2 defaults in case they are not available in user defaults
// Note, the registerDefaults does not change defaults.
[defaults registerDefaults:[NSDictionary dictionaryWithObjectsAndKeys:
 @"Joe", @"first_name",
 @"NO", @"is_married",
 nil]];
//... 

NSString firstName;
BOOL married;

// the following two calls will return the user's individual preferences,
// if they are available. Otherwise, it will just return the values we
// registered previously. Saves us some hassle!
firstName = [defaults stringForKey:@"first_name"];
married = [defaults boolForKey:@"is_married"];

That's quit difference way to do in Mac. Very interesting! Some good links about User Preference Defaults:

• O'Reily Mac DevCenter.com: Mac OS X's Preferences System (and More!)


• Apple Developer Center: NSUserDefaults Class Reference


• CocoaDev(WikiWikiWeb) article: NSUserDefaults

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SQL Server Database Mail

I use msdb.dbo.sp_send_dbmail to send email notification in SQL Server. Recently I migrated our DB to a new server. The problem I encountered is my SQL SP does not working any more.

Finally, I find out this is the SQL server configuration issues. There are some configuration settings to be done on SQL server level.

First, I have to turn the mail feature on by using the command:

  sp_configure 'Database Mail XPs', 1
  reconfigure

Next, I have to configure the Database Mail. Here is the picture to access the configuration:



where you have to create a Database Mail account and profile. Basically, the configuration contains information about mail server, SMTP Authentication. The profile will be created for you after you add a new account.

One thing you have to do in the Database Mail configuration is that to set the default profile as you will use in sp_send_dbmail so that you would not need to specify a profile.

For my case, I use this sending mail feature to send file attachment in some cases. My notification report mail contains information from DB in html format. The content may be very big. If the content is very big, it will take time to open the mail. In case of very large size content, I'll send the report as an attachment file.

By default, the file size for Database Mail configuration is 1,000,000 bytes. It is very small in most cases. I have to change it to 10,000,000 or about 10MB. This can be done in Database Mail configuration.



After all these settings, my email notification runs with success.

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ASP.Net MVC

Just watched a training video Creating Task List on ASP.Net MVC. It is very impressive. MVC design pattern has been used for Windows application and now the framework for ASP.Net is available.

I have used this or MVP in several desktop applications before and I have not touched this type of design for several month. I'm very glad to see the new package available.

MVC pattern provides very good design infrastructure with separations of UI, Controller and Model. In addition to this model, I prefer to add a Repository level to separate data base and classes. The Repository model is responsible to provide data as objects and interface for updating objects back to DB.

Any good design pattern does not resolve all the issues. Still you have to keep good practice to use them. I understand that the tutorial video is just an instruction to MVC. My comments on the practice in this video is that there are too many client to server calls. To create a new task you have to make a call to server side to add a new task. However, to mark a task as completed, I don't think that the Complete action call to server for each edit is necessary. It could be done on client side to mark one or more tasks as completed. Add a Save button to save changes. This will avoid frequent calls to server.

In order to do that, I think client side script may be needed to handle these changes. In addition to that, you have to handle redirect change by client to another page. That means a warning message to indicate changes.

New design patterns would provide a gateway to design a better applications. You should remember that that does not resolve all the problems or make your application in a good structure. It'll take time to master skills to develop good applications.

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Add Scripts to Client Side Page 3

In my first post on this topic, I mentioned that there some cases that prompts may not be desired. You can avoid prompt display for a control's click event by calling the base class's method BypassModifiedMethod().

This method actually disables the prompt display by setting the client side page level script var on click event:

  m_needToConfirm = false;

However, in case of saving failure, such as exception raised from back-end DB, a postback call may be called back to the client side with some error message being displayed. This would cause a problem: if the user redirects to another page, the prompt would not be displayed and the changes may not be lost.

To resolve the problem, I added a method ResetOnSubmit() in the base class. You should call this method on Page_Load event for postback case if you want to reset the flag variable back.

protected void Page_Load(object sender, EventArgs e)
{
...
  if (!IsPostBack)
  {
    base.ResetOnSubmit();
    ...
  }
...
}

Another handy method I added to the client side base class is DebugChanges():

protected void DebugChanges(
  WebControl wc,
  string wcEventAttribute,
  string clientIDForDisplay)
{
  string script = string.Format("javascript: displayChanges('{0}')", 
    clientIDForDisplay);
  wc.Attributes[wcEventAttribute] = script;
}

where displayChanges() is a client side javascript function registered on the client side page level. This function will display the current monitored changes and original values on a WebControl specified by control's event. You call this method in Page_Load event to add this debug feature. You can decide when the control is visible. I used a URL request parameter to enable the visibility of a control in one case. See my previous post on Using Query String Parameters in ASP.Net Page.

As I promised in my previous post, here is the source codes of ClientSidePage class.

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SQL Server Project (5)

I have written several blogs on SQL Server Projects. Here is the list of links of previous posts:

• SQL Server Project 1


• SQL Server Project 2


• SQL Server Project 3


• SQL Server Project 4

Recently we moved our SQL server from one virtual machine to a real PC SQL server. DBAs created the new server and installed a blank SQL server. After that, we had to move our DBs to the new user.

Generally, DBAs don't give us sa password. What they did is to created an appsupport user with almost as same as settings as sa for us. We use this user to back up the existing DBs and copied to the new PC for restoring.

The restoring process went very well. Almost every thing has been set up as same as the existing DBs. However, for SQL database project, as I mentioned in previous articles, some Asymetric Keks for assembly keys and Log Permissions have to be set up in master db. Fortunately, I logged the steps to do that (as I wrote in my previous articles) and restored the keys and permissions in master DB.

One thing I realized that the master DB as created by sa and our other DBs with SQL database projects were restored by appsupport. The owners of these DBs are different. As a result, I could not deploy my project to DBs. The error messages say that the owners are different and they could be changed by ALTER... I used this command to change the DB(MyDB for example) owner:

  ALERT AUTHORIZATION DATBASE::MyDB TO sa

I think that if DBs' owners are different, you cannot deploy your project from Visual Studio 2005. You have to make change to keep them in sync.

The second thing I had to do is to set DB TRUSTWORTH on:

  ALTER DATABASE MyDB SET TRUSTWORTHY ON

since I referenced System.Web.dll framework assembly in my SQL database project. Otherwise an exception would be thrown out when Ssytem.Web.dll classes are called.

The last thing is to give permissions to Windows' users since I have to use VS to deploy my project remotely to the SQL server with Windows authentication. Instead of give permissions(alter and create assembly) to one user, I created a Role on SQL server DB called as db_developers and adding my user name as a member of the role. Then I set related permissions to the role.

After all these settings, I can deply my project remotely to the SQL server DB and run the deployed assembly based ST with success.

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iPone Application: MoveMe (continued)

Finally, I finished my build of MoveMe application from scratch. That's the first demo application for beginner developers. I thought it is better if I build this application by myself. I added one piece by one piece. That's quite good experience. Since Object-C is new for me, it takes some time to gain experience.

Xcode is Microsfot VS like IDE. It is hard to compare two. My first impression is good. IB (Interface Builder) is something like .Net's new Expression Blend. As its name description, it is use for UI design and link UI components, actions(for events) to class codes. At first, I did not have any clue how to use it. I thought these connections or linking must be done through IB's UI such as property, tab or dropdown list. However, when I tried to link MoveMeView class to a component in IB's outlet, I was lost. Finally, by watching some YouTube demos on IB, I figured out the linking is done through drag with Control key and drop. It's quite innovative way. I have to understand IB or Mac's way to do it.

The second lesson I learned is that parameter names in a method has to be matched if it is a delegate method. For example, when I typed in the codes for MoveMeView.m codes, I missed i in the animation delegate method's parameter name "finished":

-(void) animationDidStop:(CAAnimation *) theAnimation finshed:(BOOL) flag

As a result, the animation of MoveMe button only works at the start and then no respond after I moved it. Finally, I found the mis-typing error. It is the signature of method not matched. In Objective-C, you can call a method on object that may not defined. It would not generate an error or cause compiling error. It is OK. That's very nice. However, it may cause some very hard find bug. After I corrected my mistake, the application finds it's matched animation delegate method, and works fine. The bug caused my animation never stopping.

Another good lesson I learned is the Frameworks in Xcode project. It is similar .Net project's References. Since I created a new iPhone project in Xcode from scratch. Xcode did not add animation framework class QuartzCore.framework, which is used in MoveMe example project. I typed in codes in MoveMeView.m file. It includes the QuartzCore's header files like this:

#import <QuartzCore/QuartzCore.h>

and when I typed animation class names and methods, Xcode does show them in intellisense. However, when I compile the application. I got some errors about references not found in xxx.o. I was confused and there was not further indication where in the codes where the error is. Eventually, I realized that it is the library files missing. I have to include animation's library into the build file. In Xcode, all the libraries are under Frameworks folder in the project.

It has been very productive period for me. I got my built MoveMe working. There are some similarities between Objective-C and .Net C#. With my knowledge and experience in .Net C#, it is not so hard to understand Objective-C. However, Objective-C does have its unique features and power. I would like to continue to learn it and to develop applications.

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iPone Application: MoveMe

I started to learn iPhone application development from Apple's iPhone Dev Center. The first application is MoveMe. The material on this application gives overall description on main items in the application, but it does provide hands-on information about how to build the application by steps.

I tried to create all the classes, resources files, and windows xib files from scratch. It is not so easy. XCode provides good IDE for coding, however, I could not find similar convenient ways as I have done .Net applications by VS.

I am still in the progress to get MoveMe build up and working. One thing I found out that the window xib file has to be specified in the Info.plist file (which is under Groups & Files->Resources):



I did not use MainWindow.xib file. Instead, I created MainMoveMe.xib file. When I first run it, I got crash exception. The problem was caused by this "Main nib file base name" in Info.plist.

After I got this window file, still I could not find a way to link delegate to MoveMeAppDelegate class in Interface Builder. Since I created this window file, I have link windows to classes through Interface Builder. Anyway, it is quite interesting experiences to learn and develop iPhone Application. I'll keep log my experiences.

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iPhone, Android and Windows Mobile

It is getting very crowed in mobile phone. iPhone from Apple is mainly for hight-end users. It is very existing mobile phone. However, it has some limitations. For example, you can only run one application at one time and limited openness in iPhone SDK APIs.

Google announced Android early this year, and formed Open Handset Alliance a group of more than 30 technology and mobile companies. It is based on Java framework. It supports multi-processes and is expected to be run over a wide range of handsets from 12 keypads low-end ones to high-end ones. The first mobile phone supporting Android is coming in just a few weeks time.

Microsoft also put a lots of investment and efforts on Windows Mobile and a few mobile companies have already used it.

I think early next year we will see more interesting mobile phones with great applications available on the market!

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Add Scripts to Client Side Page 2

I have changed the ClientSidePage class. In the following articles, I'll use my updated class as examples. It is very easy to use the class, first use the ClientSidePage class as base class, and then use the base class method MonitorChanges() to add a web control for monitoring any changes.

For example, here is the code to add a textbox control for monitoring:

protected void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  {
    base.MonitorChanges<TextBox>(MonitorChangeControl,
      CONTROL_ID_MONITORCHANGECONTROL);
  }
}

where MonitorChanges is a TextBox control placed on aspx page. It is directly accessible in the server-side code class, and CONTROL_ID_MONITORCHANGECONTROL is a constant defined in the server-side class. I prefer to define control ID in a region in a class so that can be be easily maintained in once place instead spread all over the places.

One change in the method is that it is a method with generic type T, where T is constrained with WebControl class. The first parameter is a web control or the parent control where a specified control can be found by control's ID. In some cases, you may place some web controls within a GridView's templates. Those controls cannot be directly accessible. You have find them by their parent container such as GridViewRow control. In this case, you can pass in the GridViewRow control.

With the method, I used another class to find a web control. This makes it easy to use. You don't need to add some codes to find the control. See my previous blog on Find a control in ASP.Net Page.

You can monitor as many web controls as you want. However, from my experiences, I found there are too many problems to directly monitor each editable web controls. Some times you don't know how many they. For example, a GridView control may be bound to a database with dynamical rows of data. As a result, it is very hard to maintain.

The second issue is you have to understand when to initialize these controls on the client side script. As I mentioned in my previous article, the ClientSidePage class registers two groups of scripts on client side page. One is the startup scripts, where the method assignInitialValuesForMonitorChanges() is called when the web page is loaded. However, some web controls may not have data values available in the first loading process if the control is bound to an object data source and the object will be created on server side codes. The control may be late postcalled back to set values. In this case, the client side array for initial values would be nulls. What I find out is that I have to call MonitorChanges at the time the control is bound to data on server side. Then I use another overloaded method to pass initial values to the client side script so that the array could be initialized with correct values.

protected void GridView_RowDataBound(object sender,
    GridViewRowEventArgs e)
{
  if (e.Row.RowType == DataControlRowType.DataRow)
  {
    GridViewRow row = e.Row;
    base.MonitorChanges<CheckBox>(row,
      CONTROL_ID_ISEMPLOYEECONTROL, true);
  }
}

What I find out is that I don't need to monitor each web controls. What I need is to monitor only one TextBox control. It is initialized as empty. If any other control values are changed, this monitored control's value will be something like "Some data may have been changed. Click on Save button to confirm the changes".

In order to achieve this, I added two methods on ClientSidePage class. The first one is SetScriptOnClientSide(). This method will register two groups of scripts to client side in the same way as CliendSidePage does: a group script for starup and a group script for script block. These two groups of scripts are customized scripts with a customer provided registry key. This will make sure ClientSidePage registered scripts will not be conflict with customized scripts. You add whatever scripts you want to the client side.

SetControlEventScript(). This method takes three parameters, one for WelControl object, a string for an event attribute, a string for script, and a position to indicate where to add the script to the controls' event attribute if it has some scripts defined already.

Here is one example I use these methods in one aspx web page server side codes:

private void SetScriptsForClientSidePage()
{
  string script;
  /* Monitor one text box control: MonitorChangeControl with its control ID*/
  base.MonitorChanges<TextBox>(MonitorChangeControl,
    CONTROL_ID_MONITORCHANGECONTROL);
  script = @"
<script language=""JavaScript"">
  function {0}
  {
    var v_elem = document.getElementById('{1}');
    if ( v_elem )
    {
      v_elem.value = '{2}';
    }
  }
</script>
".Replace("{0}", SCRIPT_FUNC_SomeValueChanged) /* constant for function name: "SOmeValueChaned()" */
 .Replace("{1}", MonitorChangeControl.ClientID)
 .Replace("{2}", SCRIPT_CHANGE_MESSAGE); /* Message like "Some data may have been changed. Click on Save button to confirm changes or click on Cancel to revoke changes." */
  base.SetScriptOnClientSide("script", null, script);
  
  /*Add scripts for one text box control: CurrentSales */
  script = string.Format("{0};",
    SCRIPT_FUNC_SomeValueChanged);
  string eventOnChange = "onchange";
  ScriptInsertPosition pos =
    ScriptInsertPosition.BeforeExistingScrit;
  base.SetControlEventScript(CurrentSales,
    eventOnChange, script, pos);
}

This private method is called in the Page_Load() event when the page is first time loaded: monitoring one text box control, adding client side script with a script function definition, and adding event script for a web control. After done this, I always to view the client side source to verify my scripts.

The next article will provide the codes of ClientSidePage class.

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Add Scripts to Client Side Page 1

I have read an excellent article on how to add client side scripts to monitor changes and prompt user if a redirection call is fired by Scott Mitchell. He later updated the class to disable prompt in case there is no need such as Save and leaving the page.

I have used this class in my project. I found there are some features missing and then further updated the class. In this article and later on articles, I'll discuss how to use this class.

Basically, the class ClientSidePage is used as a base class for an ASP.Net Web Page (server side codes). You can use this class to monitor changes made by client on the page for editable web controls by the method of MonitorChanges().

Here is the way how it works. This method will register two script array variables (page level) on client side, one for monitored control's IDs and another for initial values for those controls.

In order to make this to work, the ClientSidePage class registers two groups of scripts on the client side: startup script and script block. The startup script is a group of scripts that will be called when the client side web page is loaded. This is for initialization purpose, for example, setting the monitored array with initial values by a script function assignInitialValuesForMonitorChanges(), which is defined in the second script group. This function initializes the array of monitored values as original values, and set a page level variable, m_needToConfirm, to true. This is a flag for confirming changes.

The second group of script, script block, contains some client side function declarations, page level events, and variables such as variable m_needToConfirm, and function assignInitialValuesForMonitorChanges() as mentioned above. Another example is to set page event window.onbeforeunload is set to a script function confirmClose(). When a unload page request is made on client side, the window.onbeforeunload event is called. The function confirmClose() checks if the flag variable is set and any monitored control' values are changed or not by comparing control's value to the original values. If so, a prompt is displayed with a message to confirm leaving the page with two options: OK for leaving the page, and Cancel for staying.

By the way, in Google's Chrome beta version browser, the OK button is "Leave this page" and "Stay on this page" for Cancel.

Most browsers have view source option. You can view those groups of scripts by this option. I like Chrome's viewing source. It opens a new tab with page's source codes, and it is very nice to search. For example, you can search for the variables, arrays, or functions as mentioned above. The searched strings are highlighted with yellow color and there are marks on scroll bar to indicate their positions. You can easily location them and know if they exist right away. Maybe that's Google's strength: search everywhere and know where they are.

There are some cases that the prompt are not desired. For example, a user makes some changes on a page, and then click on a Save button to save changes. Normally the saving request is a postback call to the server side, where changes are saved and new/refreshed data are sent back to the client side. In this case, the prompt is not needed. Scott updated the class to handle this case. Read his articles for details.

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Mac Software Development

I have have done my software development mainly in Windows Platform, some in Unix long time ago. I have got an iMac in March this year. Since then I spend a lot of my time using it at home. I really enjoy it. Recently I have installed XCode on my Mac and watched training videos about iPhone Application Development API kit.

It is very interesting to learn Objective-C and Cocoa framework even they are very different from .Net languages and framework. iMac computer is very easy to use and very stable. From what I have seen from Apple's training materials, the Objective-C and Cocoa are also very straight forward in syntax. Objective-C for Mac applications uses MVC pattern. That's the one I have seen on Microsoft's P&P team as well. I think there are a lots similarities between both.

I'll spend some time to learn Mac application development. Maybe I'll get more and more involved in Mac software development. Enjoy the new adventure!

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Google Launches Chrome Web Browser Today

It is getting more crowded in the web browser war. I have IE that is a part of Windows, Firefox, an excellent open source browser with multi-tabs and add-ins, Safari for Mac, and others rarely used. Now Google enters the web browser competition with Chrome!

It is a positive thing for most end users for sure. I think Chrome will have some special offers for us. First, it is built based on IE but it is open source. Soon it will be available for Mac. That means that we could have alternative browser for IE in Mac with IE special features. Secondly, its infrastructure is sandbox so that each process has its own rights which mean more privacy. Another related benefit is that one process crashing would not affect others like tabs and mails.

I think the biggest thing why Google decides to have its own browser is that the current browsers have too many dependencies. Many of Google's products and great features are depending on browser and end user decisions. For example, Google released Google Gears which provides off-line browsing. That's a great feature for most end users. The browsing process would more smooth and faster. The real-time data can be updated by the back-end database store and processes when the Internet connection is available and there is need to fresh the data. However, it is an add-in. It will be up to the end user to install it. Without the installation, it would not work.

jQuery is another great feature for web browsing. It loads additional JavaScript libraries. There are already many jQuery add-ins or plug-ins available and Google shows great interest in it. However, many features will depend on end users to install them.

I guess that Chrome will install Google Gears and many other add-ins as components by default. This will make Chrome very unique and outstanding. Many advanced features will be available right away. That will shine Chrome for sure.

Welcome Chrome to the web browser world!

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jQuery

Today I read David Hayden's blog on jQuery. It is a quite interesting JavaScript library. I tried some tutorial examples and get some tastes on how to use and its initial power.

I downloaded the library jQuery-1.2.6.js source code. Then I created a test html file. I followed the instruction to save the js file in the same folder as the html file. Then I tried some example codes to hide a reference link <a...>, add a style class to the link, add a click event to the link, and some chained queries. Basically, this library provides API functions to manipulate DOM objects or elements, handle events, perform animation, and add Ajax to your web project. As David recommended, jQuary in Action is a good book for beginners.

I'll spend some time to try out and learn this great tool. Hopefully I can use this in my web projects.

Here is a training video program by a 12 years old child in google engEdu:



Here is very good reference to jQuery API libraries: Visual jQuery 1.1


50+ Amazing jQuery Examples. Unfortunately, some links are not available. However, some are really amazing web pages.

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Collection Filter Function

Let's continue the topic of my previous blog on .Net Generic and Value Data Type with an example of collection filter function for generic value data types. This function takes two collections, the first one as input collection and another one as filter collection. The returned collection will filter out all the items in the filter collection from the first collection. In this case, in order to filter items, the value data type makes sense when comparing equalities for all the items in a collection to an item. For reference data types, however, it is hard to tell equality or not, by reference or property members? You even can expect multiple-levels if some property members are reference types.

public IEnumerable<T> FilerCollections<T>(
  IEnumerable<T> list,
  IEnumerable<T> filterList)
  where T: struct
  {
  if ( list != null )
  {
    foreach (T item in list)
    {
      bool found = false;
      if (filterList != null)
      {
        foreach (T filterItem in filterList)
        {
          if (filterItem.Equals(item))
          {
            found = true;
            break;
          }
        }
      }
      if (!found)
      {
        yield return item;
      }
    }
  }
}

Here is the test program:

Test t = new Test();
IEnumerable<int> list;
List<int> list1 = new List<int>(new int [] {1, 2, 3, 4});
List<int> list2 = new List<int>(new int[] {3});
list = t.FilerCollections<int>(list1, list2);
if (list != null)
{
    foreach (int item in list)
    {
        Console.WriteLine("item: {0}", item);
    }
}
else
{
    Console.WriteLine("List is empty");
}

and the result screen:

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.Net Generics and Value Data Type

I use .Net Generics a lot. The great benefit is that you can make your codes reusable even you may use it only for one data type. You may extract the generic class or method to a library to a library for reuse. Secondly, it still keeps type safe or strong type integrity. Any attempts to use wrong type will be caught at compile time instead of run time.

The generics can be specified by where clause. In most cases I use generics for reference data types, i.e., classes. If you say a generic as class, that means the generics data type is a reference type. You can use new() to further indicate the class can be instantiated by the default constructor with no parameters. If you specify the class a specified class, that means any class which inherits from the class can be used for the generics class or method.

You cannot use more than one classes in where clause, however, you can use interfaces to specify that the generic class should implement some interfaces. Then in your generic class or method, you can safely call the implemented interfaces or methods.

How about value data types such as int, string or double as examples. You can use struct in the where clause. If you want to use the nullable value data types, you can simply use ? after the generic type, such as T?.

class Test
{
  public T GetValueOrDefault<T>(T? item) 
    where T: struct
  {
    return item.GetValueOrDefault();
  }
  public T? GetValue<T>(T? item) 
    where T: struct
  {
    if (item.HasValue)
    {
      return item.Value;
    }
    else
    {
      return null;
    }
  }
}

here are codes to call the methods:

Test t = new Test();
int? a = 2;
a = t.GetValueOrDefault<int>(a);
//t.GetValueOrDefault<Test>(t); //Error: t is not none-nullable data type
Console.WriteLine("GetValueOrDefault<int>(a) = {0}; GetValue<int>(a) = {1}", 
    t.GetValueOrDefault<int>(a), t.GetValue<int>(a));
a = null;
Console.WriteLine("GetValueOrDefault<int>(a) = {0}; GetValue<int>(a) = {1}", 
    t.GetValueOrDefault<int>(a), t.GetValue<int>(a));
Console.WriteLine("GetValueOrDefault<int>(a) = {0}; GetValue<int>(a) = {1}", 
    t.GetValueOrDefault<int>(3), t.GetValue<int>(3));

 

The result of the above codes in a console is:



Here is an interest posting on .Net Generics and a question about enum data type.

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SQL Nested SELECT Statement in FROM Clause

You can create a view by using SELECT statement. For example, a View called as AllEmployeeInfo by SQL statement: SELECT * FROM Employees. Employees is a table. That's quite simple. Then you many list all employee names hired after '2005-01-01' from the view:

SELECT FirstName, LastName
  FROM AllEmployeeInfo

Is there any way to use SQL SELECT statement as a subquery directly in FROM clause? For example:

SELECT FirstName, LastName
  FROM SELECT * FROM Employees

This does not work in Microsoft SQL 2005. However, if you name the subquery SELECT as an alias, you can do it. Here is the example:

SELECT FirstName, LastName
  FROM (SELECT * FROM Employees
          WHERE HireDate > '2005-01-01') AS Temp
-- or
SELECT FirstName, LastName
  FROM (SELECT * FROM Employees) AS Temp
  WHERE HireDate > '2005-01-01'

It looks like that SQL will create a temporary or dynamic view for the alias, then you could SELECT columns from there. Quite cool? I tried this in PL/SQL Oracle 9.0 but it does not work. Anyway, I like this quick way to get data. Sometimes you may need this kind of nested SELECTs so that you can filter data by several levels and avoid to create unnecessary views.

More on nested SQL queries, read this blog: Using a Subquery in a T-SQL statement.

Notes and Updates on this blog: Actually, the nested SELECT statement is available in Oracle or PL/SQL as well, but you don't need to AS in the statement. I got this correction from my StackOverFlow Q&A. Thanks for the correction!

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ASP.Net and Data Source Controls

In an ASP.Net page, many asp controls can be bound with a data source control, such as SqlDataSource and ObjectDataSource. I prefer to use ObjectDataSource than SqlDataSource. Here are my two main reasons.

First SqlDataSource includes a SQL statement in the control. If you change different data DB source from Microsoft SQL to Oracle DB, the SQL statement may be different. Therefore, you may have to make change in the UI aspx page or server side .Net class codes.

ObjectDataSource is binding data source from a a class's methods to get or update data. The class hides the way how data are retrieved or saved. I call it as business logic layer class (BLL). The class can be defined in another library assembly. This will make unit test much easier.

Second reason is that you don't have control how many times to call SqlDataSource to get data. For example, if you have a combo box in a GridView for product types and link it to a SqlDataSource to get product types. Each combo box will call the SqlDataSource to get product types when GridView is initialized. If there are tens or hundreds of rows in the GridView, there will be tens or hundreds call to database to get the same data. Even worse, in case of post-back calls, the GridView will be refreshed again. This may make the front UI very slow if the retrieving data process is slow.

In BLL class, you can easily cache data to avoid unnecessary calls to database. Simple define your data collection as a static List in the class. Only the first time when the page is initialized the static data member is populated with data from database. The subsequent calls will get data from the cache. You may need to define a reset method in the BLL class so that in the Page_Load event, if it is not post-back call, call this reset method to reset the static member to null. Then when the GridView is initialized, the data will be obtained from database for the first time.

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Using Query String Parameters in ASP.Net Page

You can use query string parameters in a URL request string to pass information into an aspx page. This is very common way to pass values from one page to another page. The URL query string is in the format like:

http://mypage.aspx?para1=value1¶2=value2...

I also use this mechanism to pass in additional data or flags to display some hidden values or to provide additional information from server side codes. For example, in a GridView control, normally we only display a UI table which are readable by clients, such as employee first name, last name and department. The employee ID, which is important information for server side updating, is normally a hidden column in the table.

As in this example, my codes handle some query parameters. One is "displayEmployeeID". If it is true, the employee ID then is visible:

http://mypage.aspx?para1=value1¶2=value2&displayEmployeeID=true

This parameter can be manually added the URL address text box (use & to separate parameters). If it is not available, the default value is false. Here are some codes in my aspx.cs page in the Page_Load() event:

bool display = false;
string sVal = HttpUtility.UrlDecode(Request.QueryString["displayEmployeeID"]);
if (string.IsNullOrEmpty(sVal) == false)
{
  if (!bool.TryParse(sVal, out display))
  {
    display = false;
  }
}
DataGridView.Columns[0].Visible = display;

I use the same way to display my business logic layer class's SQL string on my page so that it makes my debugging work very easy. I add a panel to the page in aspx:

<asp:Panel ID="panelDebug" runat="server" Visible="false" width="720px">
  <table width="100%"><tr align="left" ><td style="width: 110px" >
    <asp:Label ID="lblSQL" runat="server" Text="Create Object SQLs: " /></td><td>
    <asp:TextBox ID="txtSQL" runat="server" Wrap="true" Width="600px"></asp:TextBox>
    </td></tr><tr align="left"><td style="width: 25%">
    <asp:Label ID="lblUpdate" runat="server" Text="Updates: " ></asp:Label></td><td>
    <asp:TextBox ID="txtUpdate" runat="server" Width="600px" Wrap="true"></asp:TextBox>
    </td></tr>
  </table>
</asp:Panel>

Then in the event of Page_Load() and the place when my business class has retrieved data from a SQL DB:

panelDebug.Visible = GetDisplaySQL(); // method to get query parameter "displaySQL" value 
...
txtSQL.Text = bllObj.QuerySQLs; // udpate SQL by BLL class property QuerySQLs
...

Here the text box txtUpdate is as same as query SQL but for update SQL statements.

I call those query parameters as hidden parameters. They provide handy ways to get additional information about what was happened in server side, and they can also be passed in as alternative input values.

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ASP.Net: Add Client Side JavaScript Codes

ASP.Net controls do not support all the control events like window form application. For example, OnKeyUp, OnMouseUp, and OnMouseMove events. It make sense that if these events were supported, there would be too many calls from client side back server, and it would make aspx pages very very slow.

However, there are some cases you would like your aspx page to support these events. For example, I have a asp:TextBox control with an attribute of OnTextChanged event. This even only fires back to the server when you change the text and leave the control to any where on the same page. If you click on another link on the page right after you change the text, this event would not be called at all.

In order to catch this event and set a flag on the page to indicate a change, I have added another asp:TextBox control called MonitorChangeControl. Then I added the following codes in the Page_Load event to insert client side JavaScript function to the aspx page so that on the client side the MonitorChangeControl text will be changed to a text "Some values may have been changed." when my monitored textbox is changed:

string changeScript = "<script language='javascript'> function SomeValueChanged() {" +
  "document.getElementById('" + MonitorChangeControl.ClientID +
  "').value = 'Some values may have been changed.'; }</script>";
// Add the JavaScript code to the page.
if (!ClientScript.IsClientScriptBlockRegistered("SomeValueChanged"))
{
  ClientScript.RegisterClientScriptBlock(this.GetType(), "SomeValueChanged", changeScript);
}

After register the script function, then in the following codes I add an attribute "OnKeyUp" with a script call to the function "SomeValueChanged()":

TextBox myTextBox = WebPageUtil.FindControlRecursive(row, "curr_day"); //row is a GridViewRow
if (currValue != null)
{
  myTextBox.Attributes.Add("OnKeyUp", "return SomeValueChanged()");
}

When I run the aspx page in a browser, the TextBox is converted to an Input document element with an attribute like this:

<input name="..." OnKeyUp=""return SomeValueChanged()" .../>

This attribute will cause the client side event fired whenever the input element's text is changed or key-is-up.

So far so good. However, for an asp:CheckBox control, if the attribute is added in a the same way, the attribute is actually added to a span element in the aspx page which is outside of the input element (converted from CheckBox):

<span ... OnKeyUp="" ...><input id=... type="checkbox" .../></span>

Therefore, I have to add the attributes in a different way:

// row is a GridViewRow control and FindControlRecursive is my function.
CheckBox box = WebPageUtil.FindControlRecursive(row, "ValidatedCheckBox");
  if (box != null)
  {
    box.InputAttributes.Add("OnKeyUp", "return SomeValueChanged()");
    box.InputAttributes.Add("onmouseup", "return SomeValueChanged()");
  }

After that, I tried to view source from the browser. Here is the result of what I expected:

<input id=... type="checkbox" ... OnKeyUp="return SomeValueChanged()" onmouseup="return SomeValueChanged()" />

By the way, the event of OnChange is working for TextBox control but not for CheckBox controls. The OnChange is fired only after you make a change and at the moment whey you leave the control. For complete HTML element, properties/attributes, and events, see the page of HTML Event Attributes and JavaScript Event References.

For the function FindControlRecursive(), see my previous blog on May 29, 2008

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SqlContext.Pipe.Send not Available in SQL Server Project's Functions

I tried to use SqlContext.Pipe.Send to send a message back from a SQL project's funciton. It does not work at all. When the function is called, it throw an exception at the point SqlContext.Pipe.Send is called. It works fine in a SQL project' Stored Procedure.

Normally, I use this send to debug my program in the development stage. With this limitation, I have to create a stored procedure instead. After everything is fine, I then change it back to a function.

Another related issue about SQL Server Project, if I tried rename the previous deployed stored procedure as a way to back up the previous version of CLR SP, the SP is gone after I deploy my project again. It looks like that the deployment is smart enough to remove the previous version first, no matter you rename it or not. It does make sens since the new CLR assembly will be deployed and replace the old one. Even you rename it, the CLR SP should not be able to work since the assembly has been updated.

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Comparing Two Tables By SQL Stored Procedure

I have created a SQL Stored Procedure to compare any two tables based on Microsoft SQL Server 2005 new syntax EXCEPT and INTERCEPT. Basically, I used EXCEPT and UNION to get the result of differences between tables and INTERCEPT to get the same result of two tables.

In addition to that, the SP will compare two tables by specifying column fields and conditions and display the result by optional ORDER BY clause. Here is the SP:

CREATE procedure [dbo].[SP_CompareTables] (
 @table1 varchar(100),
 @table2 varchar(100),
 @table_colList varchar(3000) = NULL,
 @whereClause varchar(3000) = NULL,
 @orderByClause varchar(3000) = NULL,
 @difference0 int = 0
)
AS
  DECLARE @sql varchar(8000);
  DECLARE @colList varchar(3000);
BEGIN
  if ( @table_colList is null Or @table_colList = '' )
  begin
    set @colList = '*';
  end
  else
  begin
    set @colList = @table_colList;
  end
  if ( @difference0 = 0 )
  begin
   set @sql =REPLACE(REPLACE(REPLACE('
SELECT ''@table1'' AS TblName, *
FROM (
  SELECT @colList
 FROM @table1
 EXCEPT (
   SELECT @colList 
  FROM @table2)
) x
UNION ALL
SELECT ''@table2'' AS TblName, *
FROM (
  SELECT @colList
 FROM @table2
 EXCEPT (
   SELECT @colList
  FROM @table1)
) y', 
'@table1', @table1),
'@table2', @table2),
'@colList', @colList);
  end;
  else
  begin
    set @sql =REPLACE(REPLACE(REPLACE('
SELECT @colList
  FROM @table1
  INTERSECT (
    SELECT @colList 
 FROM @table2)', 
'@table1', @table1),
'@table2', @table2),
'@colList', @colList);
  end;
  if ( @whereClause is not null And len(@whereClause) > 0 )
  begin
    set @sql = REPLACE(REPLACE('
SELECT * FROM (@sql) v
WHERE @whereClause', 
'@sql', @sql),
'@whereClause', @whereClause);
  end
  if ( @orderByClause is not null And len(@orderByClause) > 0 )
  begin
    set @sql = REPLACE(REPLACE('@sql 
ORDER BY @orderByClause', 
'@sql', @sql),
'@orderByClause', @orderByClause);
  end;
  print @sql;
  exec(@sql);
  return 0;
END

To use this SP is very simple. For example, to compare two tables of [Employees] and [Employees_backup], you can just run the following script to compare two whole tables:

EXEC SP_CompareTables 'Employees', 'Employees_backup';

More examples by specifying columns, where clause and order clause:

EXEC SP_CompareTables 'Employees', 'Employees_backup', 'FirstName, LastName';
EXEC SP_CompareTables 'Employees', 'Employees_backup', 'FirstName, LastName', 
  'FirstName like ''D%'' AND BirthDate Between ''Jan 01, 1990'' AND ''Jul 30, 2008''';
EXEC SP_CompareTables 'Employees', 'Employees_backup', 'FirstName, LastName', 
  NULL, 'FirstName, BirthDate' , 1; -- get same results

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SQL Server Project (4)

I have to close this series articles on SQL Server Project. The final part will cover some special issues related to SQL Server Project.

The first issue is the connection to SQL server. As I mentioned in SQL Server Project (2), it is recommended to use the context connection since the CLR assembly is already in a SQL server running process. However, this connection can only be created once. You cannot create another context connection for other executions. Normally, you don't need another one in one stored procedure for example. However, if you create several SQL procedures, functions, and triggers in one dll, you might get exceptions if one calls another since only one context connection is allowed. You don't have control who is going to run these stored procedures, functions, or triggers.

Therefore, I think it is better to create one SQL item (SP, function or trigger) in one dll. You could create a normal SQL connection with catalog for a db table, user name, and password information in a connection string if you have to, and that connections can be created more than once. In a SQL server context, it does not make sense to do that unless you need to connect to another SQL server or Oracle server.

An related issue is that always to handle exceptions in your assembly and close any opened connections. As I mentioned before, the assembly is loaded to SQL server running process, and it would not unloaded automatically when your SP exits. The assembly may still in memory. If you don't handle exceptions, the opened connection will block the same SP being called again.

The second issue is that some assemblies may not work in SQL server project. I tried NHibernate and some other dlls as my references. What I found is that some assembly reflection functions are not working in SQL server. For example, I found that there always exceptions when these dlls try to load another assembly file to get class or property information. All these kind calls cause exceptions. This is very unfortunate and I think this is very bad limitation for SQL server project. I have no idea why and how exceptions would happen.

If you are going to write your SQL server project in C#, all the parameters in a SP have to be specified whey the SP is called, unlike MS Transact SQL SP could have default values for parameters.

The installation and deployment process for a SQL Server Project is a complicated one. As I mentioned in my previous articles, some asymmetric keys, log in permissions have to be created, and dependency assemblies have to be registered. The deployment of SQL server project is one click process if you have source codes and Visual Studio avalailbe. However, that click-only-once deployment may hide some SQL calls to register and set up all SPs, function and triggers. If you want to create an automation process in SQL, you have to keep all the assembly files available somewhere even they are not referenced after the installation and deployment. To uninstall it, the process is reverse. You have to remove all the SPs, functions, and triggers first, and then to delete assemblies, and then other dependency items. Since there are many things involved, anything wrong may cause your assembly not being functional.

I had a case that my CLR assembly SP did not work one day. It says about some permissions to load assembly failure. I tried to remove all the assembly and to re-install again, but I could not remove them as well. I was stuck in the middle. Finally I found it is the case SQL server was in low virtual memory. The error message actually was misleading. I restarted the SQL sever and reloaded files I did in the middle, then everything worked fine. Therefore, be prepared to handle all the uncertainties, document all the procedures in a well organized way and save all the source codes and dependency files in repository.

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SVN, Its Tools and Checkins

Subversion (SVN) is an open source version control system. I used it for source code control or repository. There are two open source SVN tools available for Windows and Visual Studio: TortoiseSVN and AnkhSVN.

Normally, I use Tortoise to check out source codes, a solution or project, to a folder and then it will create SVN client folders and files (hidden) to mark files as a copy out from a SVN reposity. Then, open the sln or project by VS. AnknSVN will detect this project is from SVN and prompt you AnkhSVN is available for use for the project.

If you make a change to a file, the file then is marked as a changed one with red icon. You can commit the change back to the SVN server or check in to the repository. Ankhn works well for editing files. However, it does not support file renaming. You have to remove the file and add a new one as two steps for renaming.

In many cases, I have to revert some changes or the whole changes by using Ankhn's context menu. Revert means no change to the file in local and re-copy the file from repository to local. In case of removing a file, you will be prompt to remove the file from the repository. If you choose Yes, this actually is commit or change to the repository! You cannot just revert the change to get it back. You have to revert to previous versions. If you have several check-ins in a day, it may be hard to find the correct one restored back. Therefore, if you want to make a trial change in local, do not remove the file from the repository. Then you can simply revert the local project back and use Update to refresh the local files if you do not want to commit the change.

If you removed file from local (not in the repository!), and verified the change is OK and want to commit you changes to the repository. Remember, the removed files are still in the repository after your check-in. Use Tortoise's repo-browser to open the repository and remove the file from the browser. That's another commit change to the repository.

In a sense, those SVN tools do not have a check out session, or SVN does not support check out set or locking a check out set. That means several developers can work on a same source code file at same time. Any developer can drop their change and that's fine for others. However, if one checks in the code file, others may have to merge their changes before check in. Ankh provides diff for comparing repository file to local files and will prompt, I think, you if your check out version has been changed by others.

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Add Colors to Codes

Today I did some change to my blog's template html page with some style sheet definitions from ASP.Net forums' colrcode.css.

To find the css file, you have to view its source codes and find link to css at the top of web page. There are several css files. To find the style definitions for programming codes, you can view the partial codes from the forum web page's program codes.

ASP.Net forums provide on-line posting editor with a tool bar to insert source codes with formatted HTML tags around programming source codes, such as C#, VB, SQL, XML, ASP.Net and others. That's why I choose ASP.Net forums' css. I can use its posting editor to get some formatted HTML codes and then post them to my blog. Since I use the same css file in my template, my source codes are marked with colors!

One color is missing in ASP.NET page: color for class, interface and intrinsic or predefined types. I added a new tag as classInterface in my template for these cases. You will see my example codes with colors!

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Calculate Number of Months from a Date

Here is a simple function to calculate number of months from a date to now:

public int NumberOfMonths(DateTime fromDate)
{
   int months;
   DateTime dt = DateTime.Now;
   months = dt.Month + dt.Year * 12 -
     (fromDate.Month + fromDate.Year * 12);
   return months;
}

It is simple and no need to add any comments. However, when I first tried to google it, I found some very complex codes to get number of months and they are not right. Finally, based those codes, I figured out that the calculation is simple.

You may use this function twice to get difference between two dates.

One note about this function is that if the input date value is a future time, the number of months is a negative value.

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Tools and Utilities

Tools and utility programs are essential helpers for programming. I learned a lots of tools from web, blogs and other people. I remembered that when I was working at one SCADA company about 7 years ago. One developer showed me Total Commander tool with his passion. He told me it is much better than Windows File Explorer and he cannot work without it.

Since then, I tried this tool and I fall in love with it. It helps a lot for file exploring, management, and software development. When I work any where, I always bring it with me.

Many other tools are also very good. Here is a list of tools Jean-Paul and Scott Handselman recommend:

• developer.tools.list


• Tools and Utlities

I like to read JP's blog. Some of his blogs recommended some really good tools.

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Find a Control in ASP.Net Page

One ASP.NET page is composed of one aspx or xml file for front-end UI design and a class either in C# or VB as server side codes related to the page and control events.

Unlike window form application, the code-behind class does not know controls on the page directly. You cannot directly access control instances. For example, a label or text box control within a GridView control's template.

Here is one function I use to get a control by id:

using System.Web.UI;
...
public class WebPageUtil
{
...
  public static T FindControlRecursive<T>(Control root, string id) where T: Control
    {
        T found = null;
        if (root != null)
        {
            found = root.FindControl(id) as T;
            if (found == null)
            {
                if (root.ID == id)
                {
                    found = root as T;
                }
                else if (root.Controls != null)
                {
                    foreach (Control ctr in root.Controls)
                    {
                        
                        found = FindControlRecursive(ctr, id);
                        if (found != null)
                        {
                            break;
                        }
                    }
                }
            }
        }

        return found;
    }
  ...
}

Where Control is a System.Web.UI.Control. It has FindControl() method. It can only find control within a container control, or root in this case. For example, in a GridView control named as GridView1, a TableCell control in a selected row (GridView1.Rows[0]) may contain some Label or TextBox controls, which are defined within aspx page GridView1 control's template.

However, this call only search for controls directly placed within the current control. If the control is within the next or even deep level, you have to loop its children Controls to call recursively.

I use generic type method call to make the method very simple to use. Here are some examples:

GridViewRow row = GridView1.Rows[e.RowIndex] // e is GridViewUpdateEventArgs object
LinkButton btnSave = WebPageUtil.FindControlRecursive<LinkButton>(row, "btnSave");
if (btnSave != null)
  btnSave.Visible = false;

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SQL Server Project (3)

In a SQL Server Project, all the SQL Server Objects (SSO), such as stored procedures (SP), must be defined as public static methods. All these methods are marked with Microsoft.SqlServer.Server Attributes, so that they can be deployed as SQL Server Objects.

Let's see how a SSO is called in SQL Sever. For example, when a SP is called first time, the SQL server will load the assembly library from the database, as I mentioned that all the assemblies have to be registered in a DB, into memory. Then the specified static method is called. After the SP finishes its job, however, the assembly stays in the memory forever. I tested this feature with a simple SP and a private static integer counter in its class. The counter increases by 1 for each call. The counter stays in the memory with its last call increment for several days.

This is a quite interesting feature of the deployed SSOs. Actually, if you think it in the context of SQL service process, it is not hard to understand it. The SQL service process loads the assembly into memory. Since static methods are global available, they will stays as long as the SQL service process stays.

However, this posts a problem most developers do not realize. They assume that when a call is finished, all the related resources should be released. If the assembly is not well designed, it may cause memory leaks in a SQL server. For example, if some resources are not cleaned, these resources are left in the memory for each call. You can imagine that if the SSOs were called constantly, it would cause memory leak. Another issue is that if some resources are static and not cleaned, these resources are occupied in memory. As a result, the first call is fine, but the next call may get exception since they cannot access these resources.

Therefore, you have to pay attention to all the cleaning jobs. Make sure that all the resources are freed after the execution, including the case of the execution being interrupted by clients. For example, you have to handle ThreadAbortException exception.

Talking about exception handling, it is not recommended to handle or hide all the exceptions. For example, if you design a Trigger, you may want some exceptions thrown to SQL server so that any related failure would cause the SQL server to roll back transactions. Therefore, if you know how to handle some exceptions, you can handle them, otherwise, leave them alone.

There is a way to clean assembly from memory in SQL server. Run the following command to clean all the unused cache and free up memory:

DBCC FREESYSTEMCACHE ('ALL')

I run this command in a daily job for cleaning memory used during a day.

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