Remote Validator in asp.net mvc 3

Remote Validator

ASP.NET MVC 3 supports the new RemoteAttribute class that enables you to take advantage of the jQuery Validation plug-in's remote validator support. This enables the client-side validation library to automatically call a custom method that you define on the server in order to perform validation logic that can only be done server-side.

In the following example, the Remote attribute specifies that client validation will call an action namedUserNameAvailable on the UsersController class in order to validate the UserName field.

public class User {
    [Remote("UserNameAvailable", "Users")]
    public string UserName { get; set; }
}

The following example shows the corresponding controller.

public class UsersController { 
    public bool UserNameAvailable(string username) 
    { 
        if(MyRepository.UserNameExists(username)) 
        { 
            return "false"; 
        } 
        return "true"; 
    } }

For more information about how to use the Remote attribute.

The above content is Taken from www.asp.net  help file read full from here