Currently it is not possible to retrieve the values of those Silverlight RichTextBox properties. This is because the Silverlight automation extension isn't aware of their types so defaults to the string type (returning the type instead of the value) if you try to access any of those.
I have submitted two feature requests for being able to access those properties of RichTextBox control here
. The more requests we get to support those the bigger the chance is those features to be scheduled for development for a future version of the testing framework as well as Telerik Test Studio.
Please let us know if there is something else we could assist with.
the Telerik team