C# difference between casting and as? [duplicate]

Possible Duplicate:
What is the difference between the following casts in c#?

In C#, is a there difference between casting an object or using the as keyword? Hopefully this code will illustrate what I mean...

String text = "Hello hello";
Object obj = text; 

String originalCast = ((String)obj).ToUpper();
String originalAs = (obj as String).ToUpper();

Thanks

:)

Solution 1:

as will never throw a InvalidCastException. Instead, it returns null if the cast fails (which would give you a NullReferenceException if obj in your example were not a string).

Solution 2:

Other than InvalidCastException that's already mentioned...

as will not work if the target type is a value type (unless it's nullable):

obj as int // compile time error.