How to test if MethodInfo.ReturnType is type of System.Void?

c# reflection methodinfo
Dead account picture Dead account · Nov 30, 2009 · Viewed 21k times · Source

Using reflection to obtain a MethodInfo, I want to test if the type returned is typeof System.Void.

Testing if it is System.Int32 works fine

 myMethodInfo.ReturnType == typeof(System.Int32)

but

 myMethodInfo.ReturnType == typeof(System.Void)

does not compile? At present Im testing if the string representation of the name is "System.Void" which seems very wrong.

Answer

Jeff Sternal picture Jeff Sternal · Nov 30, 2009

You can't use System.Void directly, but can access it using typeof(void).

Several people point out (here and in the comments here for example) that the reason for this is that the ECMA Standard 335, Partition II, section 9.4 says:

The following kinds of type cannot be used as arguments in instantiations (of generic types or methods):

  • Byref types (e.g., System.Generic.Collection.List 1<string&> is invalid)
  • Value types that contain fields that can point into the CIL evaluation stack (e.g.,List<System.RuntimeArgumentHandle>)
  • void (e.g., List<System.Void> is invalid)

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