Visual Studio Error: An item with the same key has already been added

Question

When I'm trying to change the default Image of a Control on Windows Forms in Form Designer (no matter where on which control) I get this error:

Error message: An item with the same key has already been added

I tried to delete and recreate the Resources.resx file.. I assured that only 1 resx file with these keys exist.. (in fact that's my only resource file) but it still does not work.

I have som strings in it and some images. That's all.

Any idea?

Answer 1

Was getting this error while adding a project to a solution. None of the above metioned scenarios applied but restarting visual studio fixed this. Silly, yes. Visual studio version - 2015 enterprise.

Answer 2

I had this problem too. The solution is to never create a .resx file with the name "Resources.resx" because it conflicts with the "Resources.resx" files that can be automatically created in the project's properties dialog.

Just right-click and rename the "Resources.resx" and you should be able to change images perfectly.

Answer 3

If you really want to figure out what is going wrong, you can try and attach a debugger to VS and break while devenv.exe is showing the message box. From the call stack it should be obvious what VS is doing. Here are more details about debugging Visual Studio: http://blogs.msdn.com/kirillosenkov/archive/2008/12/07/how-to-debug-crashes-and-hangs.aspx

If you like, you can post the call stack of the Visual Studio main thread here and I can try to investigate what is going on.