Question

I used LINQ to SQL to generate a dbml file which contains the database model for my database table. I want to use UIHint to let MVC present some fields as DropDownLists or Checkboxes in edit mode. But if I change the file, it will be lost if it’s been regenerated. How should I solve that issue? I’m quite new to MVC and still learning. I’ve set up a controller with views for all CRUD elements, but now I’m finetuning and I’m running into this problem.

Answer 1

Since Linq-to-SQL auto-generates partial classes, you’ll need to create a partial ‘buddy class’ where you will add your Data Annotations. Your buddy class mirrors portions of the auto-generated class that you need to modify. You tie them together with [MetadataType(typeof(BuddyClassName))] The partial buddy class and the auto-generated partial class will be merged together when you compile your project.

In an example given that:

• Your namespace is “Project.Models”

• Your Linq-To-Sql class is called “Products”

  using System.ComponentModel.DataAnnotations;
  
  namespace Project.Models
  {
    [MetadataType(typeof(ProductsMeta))]
    public partial class Products
    {
      // You can extend the products class here if desired.
  
      public class ProductsMeta
      {
        // This is a Linq-to-Sql Buddy Class      
        // In here you can add DataAnnotations to the auto-generated partial class
  
        [Key]
        public int ProductKey { get; set; }
  
        [Display (Name = "Product Name")]
        [Required(ErrorMessage = "Product Name Required")]
        [StringLength(255, ErrorMessage = "Must be under 255 characters")]
        public string ProductName { get; set; }
  
        [UIHint("MultilineText")]
        public string Description { get; set; }
      }
    }
  }
  

These articles were very helpful:

1. ScottGu: ASP.NET MVC 2: Model Validation
2. How to: Validate Model Data Using DataAnnotations Attributes
3. Validating with Data Annotation Validators