Question

I have a .NET 2.0 class the properties of which are marked virtual.I need to use the class as a model in a MVC2 application. So, I have created a .NET 3.5 class inheriting from the .NET 2.0 class and added the DataAnnotations attributes to the overriden properties in the new class. A snippet of what I have done is below

// .NET 2.0 class
public class Customer
{
   private string _firstName = "";
   public virtual string FirstName
   {
      get { return _firstName; }
      set { _firstName = value; }
   }
}

// .NET 3.5 class
public class MVCCustomer : Customer
{
   [Required(ErrorMessage="Firstname is required")]
   public override string FirstName
   {
      get { return base.FirstName; }
      set { base.FirstName = value; }
   }
}

I have used the class as the model for a MVC2 view using the HtmlFor helpers. Serverside validation works correctly but the client side validation does not. Specifically the validation error is not displayed on the page.

What am I missing, or is it only possible to do this using buddy classes.

Thanks.

EDIT 1:
I have now tried this with buddy validation classes and that doesn’t work either.

EDIT 2:
I have now worked out that the lambda expression supplied to the HtmlFor helpers is causing the problem. For e.g.

Html.TextBoxFor(m => m.FirstName) calls the ModelMetadata.FromLambdaExpression method which evaluates the DeclaringType of the MemberExpression (expression.Body) as the Customer class and not the MVCCustomer class.

I have tried changing the lambda expression to Html.TextBoxFor((MVCCustomer m) => m.FirstName) but the DeclaringType is still Customer.

Is there a way I can get the DeclaringType to be of type MVCCustomer and not Customer.

Answer 1

I have now got around this by using the new keyword on the properties in the .net 3.5 class as below

// .NET 2.0 class
public class Customer { 
  private string _firstName = "";
  public string FirstName
  {
     get { return _firstName; }
     set { _firstName = value; }
  }
}

// .NET 3.5 class
public class MVCCustomer : Customer {
   [Required(ErrorMessage="Firstname is required")]
   public new string FirstName 
   { 
      get { return base.FirstName; } 
      set { base.FirstName = value; }
   }
}

This now works as expected and the DataAnnotations attributes from the MVCCustimer class are applied correctly.

Hope this helps