I\'m trying to compile my excel addin using C# 4.0, and started to get this problem when building my project in Visual Studio. It\'s important to tell you that I haven\'t had th
If you have changed your assembly version or copied a different version of the managed library stated in the error you may also have previously compiled files referencing the wrong version. A 'Rebuild All' (or deleting you 'bin and 'obj' folders as mentioned in an earlier comment) should fix this case.