[Mono-dev] System.Reflection and C# compiler differences between Mono and .NET.

Jonathan Pryor jonpryor at vt.edu
Fri Jun 8 07:46:34 EDT 2007

Mono's (g)mcs produces different metadata for explicitly-implemented
interface members than CSC does.  Thus, a question:

Should these differences be considered to be Mono bugs?


Consider explicitly implemented methods and properties:

	using System.Collections;
	using System.Collections.Generic;

	class Demo : IEnumerator, IEnumerator<Demo>, 
			IEnumerable<Demo>, IEnumerable
		/* ... unimportant ... */

		// explicitly implemented interface members
		object IEnumerator.Current {
			get { return null; } 
		Demo IEnumerator<Demo>.Current {
			get { return null; } 

		IEnumerator IEnumerable.GetEnumerator ()
			return null;
		IEnumerator<Demo> IEnumerable<Demo>.GetEnumerator ()
			return null;

There are two significant differences between Mono's behavior and .NET's

1. Property names: (g)mcs generates TypeName.MemberName, while CSC
produces Namespace.TypeName.MemberName, e.g. IEnumerator.Current vs.

Oddly, (g)mcs generates Namespace.TypeName.MemberName for methods; it's
only properties that get abbreviated in this fashion.

2. Generics: gmcs produces significantly different member names compared
to CSC:

  gmcs: System.Collections.Generic.IEnumerable`1[[Foo, test, Version=, Culture=neutral, PublicKeyToken=null]].GetEnumerator
   CSC: System.Collections.Generic.IEnumerator<Foo>.Current

As you can see, generic parameter handling is quite different -- 
<Foo> vs. `1[[Foo, test, Version=, Culture=neutral,
PublicKeyToken=null]].  The same generic parameter handling difference 
exists for properties as well as methods.

This difference is somewhat important because it's user-visible: you can
use System.Type.GetMember(string, BindingFlags) to load
explicitly-implemented interface members on a given type, but to do so
you need to use the *same* name as is present within the assemblies
metadata.  Consequently, this means that different strings must be used
to obtain the same member depending on whether the assembly was compiled
by CSC or gmcs (the Mono/.NET runtime is irrelevant).

Again, the question:  Should these differences be considered bugs within

 - Jon

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