Question

i have a problem with my mvc3 application, i need to create some Validation stuff. but i dont have a normal model class because i have used EF with the database first approach.

i can not just open the class and write something like:

[Required]
[StringLength(10)]

how to solve this problem?

Answer 1

You could use the MetadataType attribute. So let’s suppose that EF spit at your face the following class which you cannot modify:

public partial class Foo
{
    public string Bar { get; set; }
}

Now you could extend it since it is a partial class:

[MetadataType(typeof(FooMetadata))]
public partial class Foo
{
}

and then define the metadata:

public class FooMetadata
{
    [Required]
    [StringLength(10)]
    public string Foo { get; set; }
}

Or, simply throw data annotations away and use a real validation framework such as FluentValidation.NET (which I use and strongly recommend) allowing you to express complex validation rules on your models in a fluent manner, has an excellent integration with ASP.NET MVC and also allows you to elegantly unit test your vaildation logic in isolation.