What's New in Visual Basic 14: IsNot Works with TypeOf
Years and years ago, I talked about how interfaces and inheritance were tools for making different objects look alike. Using interfaces and inheritance this way allows you to process a heterogeneous group of objects using a single variable.
In that column, I also pointed out that you sometimes needed to determine what the underlying class was for a group of objects that all looked alike to you. The TypeOf keyword is primary tool you have for determining what class an object "really" is.
However, if you were doing a negative test with TypeOf, you had to write some pretty unreadable code. This example tries to determine if the object pointed to by the cust variable is "really" a PremiumCustomer:
If Not TypeOf cust Is PremiumCustomer Then
Visual Basic 14 now lets you use the IsNot keyword with TypeOf so that you can write this more readable version:
If TypeOf sender IsNot Button Then
Visual Basic just gets better and better.
Posted by Peter Vogel on 06/11/2015 at 10:35 AM