How to solve “add/remove operation is impossible, because the code element 'Cxxx' is read only”

 With Visual Studio 2008(2005), we may meet “add/remove operation is impossible, because the code element 'Cxxx' is read only” error when we want to add a new message handler in “properties” window.

 In order to solve this issue, we shall: 

1) Close current project 

2) Enter the directory where the project located 

3) delete the .ncb and .suo file (When I meet this problem, I only delete the .ncb file, and it becomes ok.) 

4) reopen the project Then we shall can add new message handler without any issue 

 

 

from:http://blog.csdn.net/mannhello/archive/2010/01/14/5190179.aspx