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+24 A:

Nothing in VB evaluates to the default value for a given type. (See this link for details.)

For an integer comparison (which the compiler will assume from the right hand operand), Nothing will thus be 0. 0 <= 2 is true for more obvious reasons :-)

Dan Puzey 2010-07-09 12:31:26

It's also worth mentioning that Nothing is also used for null checks when combined with the Is and IsNot operators.

Justin Niessner 2010-07-09 12:33:31

For completelyness: what does the compiler with the C# code? `(object)null` does not allow comparison with an integer, `Int32` can't be null ... ?

Stefan Steinegger 2010-07-09 12:36:22

You beat me while I was looking for the answer. And you got the same link, too :P

Wayne Werner 2010-07-09 12:39:50

@Stefan Steinegger: `int` can be implicitly converted to `int?`. See http://msdn.microsoft.com/en-us/library/2cf62fcy.aspx: "The conversion from an ordinary type to a nullable type, is implicit." Therefore the code `null <= 3` will result in the following warning: Comparing with null of type 'int?' always produces 'false'. I assume such code produced a compile time error in C# 2.0.

0xA3 2010-07-09 12:48:38

@Wayne: first result from MSDN search - maybe my browser shortcut pipped you to the post ;-)

Dan Puzey 2010-07-09 12:50:07

Sounds like the equivalent to `Nothing` in C# is `default(T)` where `T` is the type.

TMN 2010-07-09 12:58:02

@Stefan/0xA3 - see my edit. I think that's what's going on with the C#.

Dan Puzey 2010-07-09 13:06:26

@Dan Puzey: See Eric's answer here: http://stackoverflow.com/questions/1972262/c-okay-with-comparing-value-types-to-null/1972317#1972317. He is talking about the `==` operator but the same holds for the `<=` operator. It has nothing to do with the `CompareTo` overload.

0xA3 2010-07-09 13:22:49

@Dan - yeah, I think it may have been the first result from a google search, too <edit> nope, it was 6th. But the first result pointing to an MSDN page

Wayne Werner 2010-07-09 13:58:03

@0xA3: Done. Some of us have to work, you know ;-)

Dan Puzey 2010-07-09 15:04:41

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Nothing != null - or does it?

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