The following procedure worked for me:
- Delete the / bin and / obj folders in the source directory.
- Restart VS (make sure the intruder is closed)
- Compile
- Open the form again in Designer. The problem must be resolved.
I am sure that removing / bin and / obj is not necessary, but I could not reproduce the error and move on to a more specific solution. (My projects are usually small enough to recompile it all doesn't really matter.)
/ -. , VS, User Control Custom Control.