strange warning about ExtensionAttribute

Question

I\'m getting a strange warning:

The predefined type \'System.Runtime.CompilerServices.ExtensionAttribute\' is defined in multiple assemblies in the gl

Answer 1

I agree with ShuggyCoUk that the best course of action is to try to remove the offending dll. That may not be possible, though.

Another way to resolve the ambiguity that the compiler is complaining about is to change the Alias of the referenced dll. In your project, in the References folder, if you click on a referenced dll you will see the Aliases property. By default, this is "global", which allows you to do things like "global::SomeNamespace.SomeType". You might simply be able to change the alias to something else.

This fixed a problem I had where I needed to reference Microsoft.Scripting.Core.dll, but it contained some types that conflicted with mscorlib.dll. I changed the Aliases property to be "ThirdParty" instead of "global", and that fixed the warning.