typeof(System.Enum).IsClass == false

问题:

Founded that:

typeof(System.Enum).IsClass == false

It's become strange that System.Enum has also .IsValueType == false, but Reflector shows that it is really just an abstract class.

System.Enum is a reference type like a System.ValueType and casting enumeration values to/from System.Enum reference caused boxing/unboxing. No surprises here.

But what is a reason for Type class not to tell truth about System.Enum nature? There is no anything extraordinary with the System.Enum type's reflection behavior to make it looks like not a reference type.

回答1:

It's an issue with .Net 1.1 and 2.0. I haven't checked it in 3.0

From MSDN User David Bernstein

The IsClass property of the System.Enum type returns "false", even though "System.Enum" inherits from "System.ValueType" and "typeof(System.ValueType).IsClass" return "true" (as expected). At the same time, typeof(System.Enum).IsValueType returns "false" as expected. This observed behavior seems to contradict the explicit documentation above which stipulates: "This property returns true for Type instances representing Enum and ValueType." I found this to be the case in both frameworks 1.1 and 2.0.

回答2:

I happened to recently revisit this problem under CLR4 and guess what, it is fixed now. The following definitions:

public struct SomeValueType{}

public enum SomeEnum
{
    FirstElement
}

with this program

Console.WriteLine( typeof( Enum ).IsClass );
Console.WriteLine( typeof( SomeEnum ).IsClass );

Console.WriteLine( typeof( ValueType).IsClass );
Console.WriteLine( typeof( SomeValueType).IsClass );

Yields the following results:

CLR2: False, False, True, False 
CLR4: True, False, True, False