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1. Compile and run the following Program.cs, targeting .NET Framework 4.5
public class Program
public static void Main(string args)
var method = typeof(MyOwnClass).GetMethod("Foo");
var parameter = method.GetParameters().ParameterType.GetElementType();
var genericTypeDefinition = parameter.GetGenericTypeDefinition();
public abstract class MyOwnClass
public virtual void Foo<T>(List<T> action)
/* ... */
This is not a bug, mono uses a differently named c# type internally to represent type objects. This is an implementation detail.
However it caused problem as these two types behaves differently. For example, calling GetTypeInfo() off a Mono type throws as it is not an IReflectableType.
Mono has System.RuntimeType too, just not in this specific code (where T is the open type parameter in an array of a generic type?)
This has caused some Castle.Core unit tests to fail only on Mono runtime.
It looks like the Castle.Core test failures are caused by a different reason. See discussion at https://github.com/castleproject/Core/issues/160#issuecomment-199788363.