I really like WPF converters. I often don’t need the ConvertBack method though.

Most programmers deal with this by leaving the throw new NotImplementedException() , or they return null.

I also see this method being marked with the [Obsolete()]  attribute. I think this totally gives you the wrong impression that it should not be used anymore.

The attribute is used to inform programmers , not the databinding system.

And of course, the method is still valid and might get a different implementation later on.

Check out the DependencyProperty.UnsetValue.