C# – the difference between casting and using “as” in C#


If there is a difference, what is the difference between the two ways of doing the following cast?

In this case e is a GridViewRowEventArgs object.

GridView gv = (GridView)e.Row.FindControl("gv"); //first way

GridView gv2 = e.Row.FindControl("gv") as GridView; //second way

Best Solution

The differences are:

  • If a cast fails, it throws an InvalidCastException.
  • If the as operator fails, it just returns a null reference.
  • You can't use as with non-nullable value types (e.g. you can't do "o as int").
  • The cast operator is also used for unboxing. (as can be used to unbox to a nullable value type.)
  • The cast operator can also perform user-defined conversions.

EDIT: I've written elsewhere about when I feel it's appropriate to use which operator. That might be worth a read...