CancellationToken UnRegister Action

CancellationToken.Register returns a CancellationTokenRegistration instance. If you call Dispose on that instance, your registration will be removed.

You can safely dispose the entire CancellationTokenSource. Without worry about unregister callbacks.

Code: https://github.com/microsoft/referencesource/blob/master/mscorlib/system/threading/CancellationTokenSource.cs#L552

The Dispose() method of the CancellationTokenSource will call dispose on every registered callback you added into your Token via Token.Register(callBack).