CLR via note 4.2 type conversion is and as difference

The IS and as operators are used for coercion of type conversions.

Is: Checks whether an object is compatible with other specified types and returns a bool value that never throws an exception

        Object o = new Object ();

        If (O is Label)
         {
             Label lb = (label) o;

             Response.Write ("type conversion succeeded");
         }
         Else
         {
             Response.Write ("type conversion failed");
         }

In the above code, the CLR will actually check the type of two objects, the IS Operation Mr. Foo Check once, if O is compatible with lable, then the (Label) O will be checked again, the efficiency is low, is not recommended to use

As: is the same as coercion type conversion, but never throws an exception, that is, if the conversion is unsuccessful, NULL is returned

        Object o = new Object ();

         label lb = o as Label;

         if (lb = = null)
         {
             Response.Write ("type conversion failed");
         }
         Else
         {
             Response.Write ("type conversion succeeded");
         }

In the above code, the CLR will only perform one type verification, which is more efficient than the IS

CLR via note 4.2 type conversion is and as difference