Question

Rails has a very convenient uniqueness validation.

ASP.NET MVC doesn’t.

I need to make sure that the e-mail address a user has entered hasn’t been registered by anyone yet.

I can see only one way of doing this kind of validation: create a new data context object in the UniqueAttribute class.

But I’m afraid that wasting memory on a new data context object just for one validation is dangerous.

Am I wrong? Is there a better way to do that?

Update

This is what I got so far

public class UniqueEmailAttribute : ValidationAttribute {
    public override bool IsValid(object value) {
        DataContext db = new DataContext();
        var userWithTheSameEmail = db.Users.SingleOrDefault(
            u => u.Email == (string)value);
        return userWithTheSameEmail == null;
    }
}

// Usage
[UniqueEmail(ErrorMessage="This e-mail is already registered")]
public string Email { get; set; }

There are two problems.

1. It would be good to have just one UniqueAttribute class, not separate classes for e-mails, usernames etc. How can I do that?

2. Creating a new data context every time you need to validate a single attribute.

SOLUTION

So in the end I created a unique constraint on the table and now I just have to intercept SqlException in Users repository. Works great and is probably more efficient than searching for the same node in the whole table. Thanks!

Answer 1

A foolproof way of doing this is to create a validation attribute that would query the database for the email address. It would certainly add latency.

An alternative would be to create a unique constraint on the table and intercept SqlException.