Question

I am working on an mvc3 application and having some problems with getting validation to work as I want.

The application is using buddy classes for the models. (This is something I haven’t used in the past and I am a little confused why they are used…anyway)

I want to add required fields to ensure data been submitted is correct. I have tried adding the required field to the buddy class.

When I submit the form no client-side validation takes place and the debugger steps into the entity frameworks generated code. Here is complains that the fields that contain null values are causing are invalid. If I step through all of those it finally gets to the controller where my if (ModelState.IsValid) is showing false.

I have client-side validation switched on.

Am I meant to be applying the data validation at the buddy class level or at the view model?

One other question is why use buddy classes? to me they seem to over complicate things.

Updated added an example of the buddy class

[MetadataType(typeof (CustomerMetaData))]
public partial class Customer
{
    public string Priorty
    {
        get
        {
            var desc = (Priority) Priority;
            return desc.ToString().Replace('_', ' ');
        }
    }

internal class CustomerMetaData
{
    [Required]
    [DisplayName("Priorty")]
    public string Priorty { get; set; }

Answer 1

Buddy classes are metadata classes to put data annotation attributes when you are not in control of the original class i.e. can’t edit it. Typical situation is when the class is generated by an ORM like Entity Framework.

//Can't edit this class
public partial class YourClass{
  public string SomeField {get; set;}
}

//Add a partial class
[MetadataType(typeof(YourClassMetadata))]
public partial class YourClass{
}

//And a metadata class    
public class YourClassMetadata
{  
  [Required(ErrorMessage = "Some Field is required")]
  public string SomeField {get; set;}
}

are you sure that you have [MetadataType(typeof(YourClassMetadata))]?

More about buddy classes here and here