I've just make a ticket: I hope, that You will find what is wrong with my code - "Your ticket ID is: 517625"
After set binding in codebehind:
Grid g = content.Content
TextBox t = g.Children
Binding binding =
binding.Source = content.ObserverDefinitions;
everything is done properly. So dynamic binding is not working in wp7 (this is my final thought, but I still wait for You answer about my SampleApp)
Have a nice day!