Skip implementation generation for proxy methods.

src/Generator/Generators/CSharp/CSharpTextTemplate.cs

@@ -1170,6 +1170,9 @@ namespace CppSharp.Generators.CSharp
 
             WriteStartBraceIndent();
 
+            if (method.IsProxy)
+                goto SkipImpl;
+
             if (@class.IsRefType)
             {
                 if (method.IsConstructor)
@@ -1201,6 +1204,8 @@ namespace CppSharp.Generators.CSharp
                 }
             }
 
+            SkipImpl:
+
             WriteCloseBraceIndent();
             PopBlock(NewLineKind.BeforeNextBlock);
         }