Integrating Validation with the Entity Framework: Listing 2.

Throwing an exception for a Changing method.

namespace northwindModel
{
  public partial class Customer
  {
    partial void OnCityChanging(string value)
    {
      if (value.Length > 25)
      {
        throw new Exception(
          "City name must be less than 26 characters long");
      }
    }
  } 
}

About the Author

Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.