Your code uses the clipboard viewer chain to get notified about clipboard change events and misuses that to prevent other applications that have registered themself to the chain from being notified.
But that solution has three drawbacks:
- The clipboard can be accessed by any application at any time
- Applications that are in the chain before your application are still getting notified
- Most applications did not even use the clipboard chain
So using such code is rather useless. It will not work reliable even when you only want to avoid the notifications being send to other applications from the chain because some will still get them.