ValueType and operator!=

Krzysztof Żelechowski 21

I have the following result:
((System.ValueType) 0) != (System.ValueType) 0 && ((System.ValueType) 0) .Equals (0)
The former is a bit unexpected. What should I make of it?

Karen Payne MVP 35,116 Reputation points

2021-09-21T08:58:10.527+00:00

Can you provide a small code sample to how the code is used?
Krzysztof Żelechowski 21 Reputation points

2021-09-21T16:02:16.24+00:00

It is not used because it does not work:
Debug .Assert (new Enum [] { ConsoleColor .Black } [0] == (Enum) ConsoleColor .Black);
P a u l 10,406 Reputation points

2021-09-21T18:53:07.897+00:00
If you hover over the "==" of this expression in Visual Studio it might help you see what's going on:

Debug.Assert(ConsoleColor.Black == ConsoleColor.Black);

You should see this in the popup:

bool ConsoleColor.operator ==(ConsoleColor left, ConsoleColor right)

So it's using the implementation of the equality operator that's automatically available to enums.

If you hover over the double equals in your example above you should see:

bool object.operator ==(object left, object right)

This is because Enum hasn't defined an equality operator, and because it's a class it's falling back to object's implementation.

Since you've boxed the ConsoleColor on both sides of the expression inside an Enum the implementation of object's equality operator does it's default reference equality check against the two boxes and returns false.
Krzysztof Żelechowski 21 Reputation points

2021-09-22T09:32:52.597+00:00

Does that mean that Enum itself is a reference type? This is a good point, it was not clear in the documentation, thank you!
I still cannot see why ValueType .Equals is overridden but ValueType .operator== is not. It seems inconsistent.

Accepted answer

Viorel 112.5K Reputation points

2021-09-21T16:14:40.483+00:00

I think that since ValueType is a class, your code creates three different objects (instances). Although, the content of these instances is similar.

Calling ‘!=’ on different objects (references) gives True. (It does not compare the contents of the objects in this case).

Calling Equals returns True because it is designed to compare the contents.

See also: “Boxing”.
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ValueType and operator!=

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