Question

I would like to validate that a username is not already in use when adding or editing a user in my solution.

Here is what I do with the remote validation:

ViewModel:

    [Required, Remote("UserNameAlreadyExists", "User", Error="Already exists!")]
    public string UserName { get; set; }

Controller:

    public ActionResult UserNameAlreadyExists(string userName)
    {
        var user = _requestServiceClient.GetUserFromUserName(userName);
        return Json(user == null, JsonRequestBehavior.AllowGet);
    }

It works pretty well for the creation. But It doesn’t work with edition because the username already exist for the edited user himself. Do you know what I mean?

A solution would be to check in DB based on UserName and UserID. So in the case of editing a user, we can check that the username does not exist yet (except the userid passed as parameter). Is it a good alternative? How to pass this userID in the Remote validation attribute?

Thanks.

Answer 1

If your users cannot change their username after creation then use a different view model for the editing where you just display the UserName without any validation.

Otherwise you can use the AdditinalFields property to pass extra data to your validator:

public class UserModel
{
    public int Id{ get; set; }

    [Required, Remote("UserNameAlreadyExists", "User", AdditionalFields = "Id")]
    public string UserName { get; set; }
}

public ActionResult UserNameAlreadyExists(string userName, int id)
{
    var user = _requestServiceClient.GetUserFromUserNameAndId(userName, id);
    return Json(user == null, JsonRequestBehavior.AllowGet);
}

You will also need to include the Id property in your form eg:

@using (Html.BeginForm())
{
    @Html.HiddenFor(m => m.Id)
    @Html.TextBoxFor(m => m.UserName)
    @Html.ValidationMessageFor(x => x.UserName)
    <input type="submit" value="Save" />
}