title: Is this a crazy way to handle multi Validation types with IDataError and WPF?
body: <p>We are using the standard method for our controls to report broken BO rules. This is done via the interface IDataError in our BO’s and in XAML the control is bound to the BO’s property etc. This approach works OK. But we need to show 2 types of visuals in the UI depending on the type (or category if you like) of the invalidation error. If it’s a required field then we show a CueBanner (water mark) but for other types we change the colour of the controls boarder. In both scenarios we set the tool type of the error message.</p>
  
  <p>The Problem with IDataError is that it doesn’t support a method/property to distinguish between error types.</p>
  
  <p>The only way I can do that is by examining the error text, required field text must contain the key word “required”. The following approach doesn’t feel right but it’s the only way I can determine the type of error and then deal with it accordingly. All required field rules must have as part of the error text “required field”.
  To make this all work I have created a custom dependency property called ErrorMessage. In my ResourceDictionary I have a Style.Trigger for Validation.HasError. In there I set my dependency properties value to the ErrorContent. Now when my dependency properties value changes I can examine the text and set the Validation.SetErrorTemplate( myControl, newErrorTemplate) to the template to suit the error type. I have to wire up a few events to the control such as lost and got focus to manage removing or adding the cueBanner template but the whole thing will work. It’s just that I’m not sure it’s the best way to do it.</p>
  
  <p>PS. When I set the ErrorTemplate i’m doing this in code, thats building and adding it. Is there a way to point Validation.SetErrorTemplate to a static resource keeping in mind that I need to switch between at least 2 types?</p>
  
  <p>Your thoughts please..</p>