Remote attribute in asp.net mvc – in some situations restricts our model

I’ve got an unexpected situation when using Remote Attribute in ASP.NET MVC3.

The model type I used:

using System;
using System.Web.Mvc;
using System.ComponentModel.DataAnnotations;

namespace dTweets.Models
{
    // at first time, user should create his account with unique username
    // as in twitter.com, user do
    public class UserMetadata
    {
        [HiddenInput]
        internal int Identity { get; set; }


        [Remote("IsUserExist", "Account")] // at any HttpPost, username should
                                           // be unique – not appropriate if 
                                           // updating/editing this model later

        [Required(ErrorMessage = "username should be unique")]
        public string UserName { get; set; } // user cannot change it, later


        [DataType(DataType.Password)]
        public string Password { get; set; } // user can also change password, later


        [DataType(DataType.MultilineText)]
        public string Abou开发者_如何学Got { get; set; } // Optional field – user can edit it later
    }

    [MetadataType(typeof(UserMetadata))]
    [Bind(Include="UserName, Password, About")]
    public partial class User
    {
    }
}

Remote attribute validates user unique name at account creation time. But when later user wants to update/change his account, Remote attribute did not allow to update model if keeping user unique name the same one.

This is not appropriate result because rarely user changes their unique user name. They just change other fields like About field or password etc.

[Note: at account creation time, I want to check user unique name so I used Remote attribute here, but at later time when updating user account I no longer need Remote attribute]

I must remove Remote attribute for updating this model later.

I want to update/change this model without changing user unique name (remote attribute is applied to this unique name).

one way to do this is to send ID value of this record in AdditionalFields named parameter like

[Remote("IsUserExist", "Account",AdditionalFields = "Identity")] 

and then you can check for uniqueness across all rows except the ones that belong to current user. and don't forget to change signature of IsUserEsists action result to receive Identity like

public ActionResutl IsUserExists(string UserName, int Identity)
{

}

Can't you just change server side validation method to something like:

public ActionResult IsUserExists(string userName) 
{
     if (!UserService.UserNameExists(userName) || (CurrentUser.UserName == userName))
     {
          return "Yeah. Is it valid.";
     }
}

You have current user, because he is logged in. As long as user can only edit his data, this will work.

This is one place where buddy metadata falls short.

Edit/Add scenarios require their own view models. One size fits all scenario validation attributes only work in very trivial business CRUD apps. Add and Edit actions happen in totally different contexts and are only transiently related. This concept is very similar to the DDD bounded context idea.