Probably you are not doing anything wrong. Keep in mind first that it is better to use CheckState instead of IsChecked in these situations. You can examine this blog post
which describes the differences in these properties. On the other hand, there is an unimplemented feature that we plan to implement after the official Q2 2011 ( mid- July). You can examine it and vote for it here
. Currently when using Style Bindings (WPF)/ ContainerBindings (SL) you have to implement your TriStateLogic on your own.
Please let us know if you need more info on this.
All the best,
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items