How can I handle a Validation.Error in my ViewModel instead of my View's code behind?

Question

I\'m trying to get WPF validation to work within the MVVM pattern.

In my View, I can validate a TextBox like this which gets handled by the code-behind method \"Hand

Answer 1

I don't know if this will help you, but I'll offer it all the same.

Also, I'm using Silverlight, not WPF.

I don't specify any validation in my Views, neither in the code behind nor the xaml. My View has only data bindings to properties on the ViewModel.

All my error checking/validation is handled by the ViewModel. When I encounter an error, I set a ErrorMessage property, which is bound to the view as well. The ErrorMessage textblock (in the view) has a value converter which hides it if the error is null or empty.

Doing things this way makes it easy to unit test input validation.