One of the good grid controls in WPF world belongs to Infragistics. With all the bells and whistles, there are still some limitation, some are WPF engine limitation and some are not. One thing that is very limiting is validation of data prior them being added to datasource. This is rather a broad subject, but I intended to use NHibernate entities (POCO objects) decorated with NHiberante validator attributes to do the validation for me. 

Simplest way to do Validation in WPF is usually implementing IDataErrorInfo interface, and do the validation in the indexer's getter. It turns out to be ugly and gets out of hand when your model / viewmodel gets a little larger. A better way would be to use NHibernate Validator engine to validate our view models. 

When using ajax forms in ASP.NET MVC the built-in Validation result (ModelErrors) won't work because of a simple fact: The built-in validation will take place when the page is being rendered on the server. When you use ajax and callbacks page will not re-render on the server-side, hence validation can not mark fields with error and add validation information to the already rendered page.