Designer cs file not updating
The issue, most likely, has to do with your auto-generated file somehow being disconnected from the control.
So for anyone else that experiences the same problem, try moving your using statements after the namespace declaration.
Every time you make an update or change the file and then press save, Visual Studio pushes those updates into this auto-generated file.
The control is never actually deployed; instead the code files are packaged into an assembly and added to the GAC, creating the web part in Share Point.
If you’ve ever created one of these Visual Web parts you’ve probably noticed that there is a code behind cs file and another odd file with a ascx.extension.
This file is automatically generated by Visual Studio and is quite important.
Visual studio 2010 not generating new control definitions in designer file Visual Studio 2010 Designer File Not Updating This seems to me to be related to the Application Page template, as the Designer works fine for user controls in the same project, and the Application Page template doesn't allow Design View. The designer file is registered in the project file, but fails to function as expected. Either of those should force VS to regenerate the designer file. here is a trick for this little problem: add a user control to your project.