Value="{Binding Path=MainProgressValue, UpdateSourceTrigger=PropertyChanged}"

window.DataContext = context;
 if (owner != null)
       window.Owner = owner;
 resultHandler = new ViewModelBaseClass.ResultHandler(context_RequestClosing);
 getDialogResultHandler = new ViewModelBaseClass.GetDialogResultHandler(context_GetDialogResultAction);
 context.RequestClosing += resultHandler;
 context.GetDialogResult += getDialogResultHandler;
 window.Show();