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.