Which is better - (int)value or value as int?

Question

Possible Duplicate:
Direct casting vs 'as' operator?

Can someone explain the difference to me and which one is better to use? I know in some situations I can only use one or the other.

(int)value

value as int

Answer 1

The latter is invalid. You can use

value as int?

if you need to "convert if possible". That's slower than

if (value is int)
{
    int x = (int) value;
    ...
}

though. That's what you should probably use if you're not confident that value is actually an int. If, however, your code is such that if value isn't an int, that represents a bug, then just cast unconditionally:

int x = (int) value;

If that fails, it will throw an exception - which is generally appropriate for a bug.

Answer 2

I value as int will cause a compiler error because operator must be used with a reference type or nullable type ('int' is a non-nullable value type). So when dealing with structs, you always use (int)value and with Objects, I prefer obj as SomeType because it is clearer and more straight to the point, plus it handles exceptions automatically (if an error occurs during casting the operator returns null).