Binding DataContext to ValidationRule

Question

I have a custom ValidationRule that requires access to the ViewModel in order to validate a supplied value in conjunction with other properties of the ViewModel. I previously tr

Answer 1

I have just found a perfect answer!

If you set the ValidationStep property of the ValidationRule to ValidationStep.UpdatedValue, the value passed to the Validate method is actually a BindingExpression. You can then interrogate the DataItem property of the BindingExpression object to get the model to which the Binding is bound.

This means that I can now validate the value that has been assigned along with the existing values of other properties as I want.