Hi Joerg Hermann,
you are getting this exception because you are indeed trying to work with two different scopes. To avoid this you should not create a new instance of the scope but use the current one instead. This can be done by modifying your code a little:
|IObjectScope scope2 = ObjectScopeProvider1.ObjectScope();
This way you will get a reference to your current scope instead of creating a second one.
All the best,
the Telerik team