Question

Possible Duplicate:
C# okay with comparing value types to null

Consider the following code with the TimeSpan, which is a struct:

// will not compile - illegal
TimeSpan ts = null;  

However, the following code does compile and is legal, though the expression is always false:

if (ts == null)
    Console.WriteLine("this line will never be hit");

Can someone tell me why it’s invalid to set a struct to a NULL, but it’s ok to compare it to one?

Answer 1

Fails to compile for me:

struct Foo { }

class Program
{       
    static void Main( string[] args )
    {
        var f = new Foo();
        if( f == null ) { }
    }
}

Error 1 Operator ‘==’ cannot be applied to operands of type ‘ConsoleApplication3.Foo’ and ‘null’