Is is possible to use a combination of ValidationRules and INotifyDataErrorInfo for wpf validation?

Question

In WPF there are 3 ways to do validation:

• Validation Rules
• IDataErrorInfo
• INotifyDataErrorInfo

Is it possible to use a combination of these at the same time? For my needs, I would like to validate new rules with the flexibility of INotifyDataErrorInfo, but don't want to interfere with existing ValidationRules for the same object I want to validate.

Answer 1

1. Mixing the different source of errors

Yes you can mix the three kind of Validation you quote :

• ValidationRules are fine for GUI(surface) validation
• IDataErrorInfo is implemented on the view model/business object. It is fine for more business oriented validation
• INotifyDataErrorInfo is also implemented on the view model/business object. It adds possibility of multiple errors on a given field and also adds asynchronous validations (ie a server or a thread can take time to answer to the valildation).

That last source of error is really more longer to implement

2. Taking errors into account

The most difficult is to take into account the different sources of error when you want to prevent a window from being closed if data is not valid.

ValidationRules error must be looked up in the GUI bindings, because the invalid data doesn't get to the business object/ViewModel.

IDataErrorInfo and INotifiDataErrorInfo can be looked in the ViewModel layer.

Regards