Validation

There seems to be four ways to go with validation with WPF:

1. Use IDataErrorInfo
2. Use custom classes with ValidationRule
3. Combine 1 and 2
4. Roll your own

What do I mean by each of these, and why?

1. Use IDataErrorInfo. You canimplement this interface in your business objects and you get the opportunity to specify validation for each property or for all properties. You do this in (usually) a general purpose method that does validation for all of your properties in your business object. This is good if you need validation for a business object, but not across objects. You can tell wpf to use it (in v3.5) by specifying ValidatesOnDataErrors=”True” in your binding specification.
2. Inherit a class from ValidationRule, and provide an override for the Validate method. You could do this for either a particular business object, or across a number of objects. You can use it in xaml by specifying it in the binding’s ValidationRules collection.
3. Do 1 for business object validation, and 2 for any validation that needs to be done across business objects
4. Do this when you need to extend the validation, e.g. like in the CSLA.Net framework