Why is this a valid comparison [duplicate]

Question

Here is some example code:

static DateTime time;
if (time == null)
{
/* do something */
}

Since DateTime cannot be null, why does this code compile?

Edit: The issue is not just that this code will always return false,but why something like DateTime which is never null is allowed in such a comparison.

Answer 1

Although time is of a non-nullable value type, it can be converted to nullable and compared to null. The comparison would yield false, which is a valid outcome.

This does not mean, however, that it is a good code. Tools, such as re:sharper, would flag this line with a warning saying "Expression is always false".