I know that MVVM purists say that you should not use messageboxes and Dialogs in a MVVM application , however as a business developer you must sometimes blok the GUI to let the user pick an item or confirm there actions .

After some discussions in the comunity i decided to show you my solution wich works fine for me and does allow unit testing in a verry simple efective way the idea is to use the MainWindowViewModel as a singleton for the child viewModels , comunication is done with delegates and my implementation of dispatching through the object pointer to get the answer back .

I documented and tested this example , it is written in VS 2010 TFS sp1 ofcourse in VB.Net