title: Data Validation with MVVM-Light WPF and Linq to Entity Framework
body: <p>I think I have read every article google returns when I search wpf mvvm-light data validation and I dont know which way to go.  I am aware of josh smith, Karl Shifflett's, and MVVM LIGHT's own demo techniques for data validation.  What I see is that most validation requires me to fully "re-abstract" my model in my view model.  Meaning that I have to create a property in my viewmodel for each property of my model that I want to validate (and in some cases convert all these into string values for binding/validation).  This seems like a lot or redundancy when all I want to do is mark most fields as required.  </p>
  
  <p>I am using LINQ to entity framework(with self tracking) for my model classes which come from a SQL server DB.  As a result I would prefer to keep my business data validation/rules within my viewmodels.  I write a simple service interface to get the data from the model and pass it to my viewmodel.</p>
  
  <p>Most of the examples I can find are from as far back as 2008 (ie josh smith).  Are these techniques still valid or are there more up to date best practices for mvvm data validation with .NET 4.5 etc.</p>
  
  <p>So I am asking:</p>
  
  <p>1) What methods do you suggest I use
  2) What methods work best in a LINQ to EF with MVVM-Light Environment.
  3) EDIT: I want to provide feedback to user as they enter data, not just when they submit form </p>
  
  <p>thanks</p>