It seems that the XAML in MVVM pattern has difficulty to pop-up a Messageboxes. My client insists that the validation labels and colors are not good for them. They still want a messagebox. How can do it?

I know I can pop-up messageboxes in the view-model, but it violates the whole purpose for the view-model. I can also raise a error, and pop-up a messagebox in some exception handlers, but the messagebox is not an exception. It is part of the normal program flow.

Is there a good way to do it in XAML? My client likes messageboxes. She does not care about the MVVM pattern, she never had any quality problem before using MVVM and unit test. But now, she can not even get her messageboxes, so she is not very happy.

Your help is definitely appreciated ... I need to make her happy.