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401

answers:

2

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.

+4  A: 

When I build this, I get the error:

System.Void cannot be used from C# -- use typeof(void) to get the void type object

Sounds like that's the answer...

siz
Yep, I fail. Would have accepted RTFM answer also :)
Dead account
+3  A: 

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)
Jeff Sternal
Im such an idiot. The error message says "use typeof(void)".
Dead account
No more hiding the error window! ;) But it is awfully strange.
Jeff Sternal