Home - About me - Browse by categories

[En][ASP.NET MVC] Remote attribute and asynchronous validation

As you probably know ASP.NET MVC supports .NET Framework 4 Data Annotations to validate user’s inputs (Required, StringLength, Range, RegularExpression…)

Another attribute exists and allows asynchronous client side validation. It’s the Remote attribute. For example, it can be used to validate e-mail and username in a registration form and alert the user before the form is posted.

Here is a sample model for a registration form :

public class UserModel
[Remote("CheckUsername", "RemoteValidation", ErrorMessage = "This username is already used.")]
public string Username { get; set; }

[Remote("CheckEmail", "RemoteValidation", ErrorMessage = "This e-mail is already used.")]
public string Email { get; set; }

public string FirstName { get; set; }

public string LastName { get; set; }

public DateTime BirthDate { get; set; }

As you can see in the previous code snippet, the Remote attribute takes two parameters :

The controller :

public class RemoteValidationController : Controller
private readonly string[] _existingUsernames = {"beedoo", "julien", "jcorioland"};
private readonly string[] _existingEmails = { "[email protected]" };

public JsonResult CheckUsername(string username) {
bool userIsAvailable = !_existingUsers.Contains(username);
return Json(userIsAvailable, JsonRequestBehavior.AllowGet);

public JsonResult CheckEmail(string email)
bool emailIsAvailable = !_existingEmails.Contains(email);
return Json(emailIsAvailable, JsonRequestBehavior.AllowGet);

These actions are very simple : they take the input to validate as a string parameter and return a Json-serialized Boolean that indicates if the input is valid or not. For this article I’ve used two arrays to represent users and e-mails databases but it’s possible to execute any code here.

The view :

@using (Html.BeginForm())
<div class="editor-label">@Html.LabelFor(m => m.Username)
<div class="editor-field">
@Html.TextBoxFor(m => m.Username)
@Html.ValidationMessageFor(m => m.Username)

<div class="editor-label">@Html.LabelFor(m => m.Email)
<div class="editor-field">
@Html.TextBoxFor(m => m.Email)
@Html.ValidationMessageFor(m => m.Email)

<div class="editor-label">@Html.LabelFor(m => m.FirstName)
<div class="editor-field">
@Html.TextBoxFor(m => m.FirstName)
@Html.ValidationMessageFor(m => m.FirstName)

<div class="editor-label">@Html.LabelFor(m => m.LastName)
<div class="editor-field">
@Html.TextBoxFor(m => m.LastName)
@Html.ValidationMessageFor(m => m.LastName)

<div class="editor-label">@Html.LabelFor(m => m.BirthDate)
<div class="editor-field">
@Html.TextBoxFor(m => m.BirthDate)
@Html.ValidationMessageFor(m => m.BirthDate)

<input type="submit" value="S'enregistrer" />

To activate the client side validation the following jQuery plugins should be loaded :

<link href="@Url.Content("~/Content/Site.css")" rel="stylesheet" type="text/css" />
<script src="@Url.Content("~/Scripts/jquery-1.5.1.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery-ui-1.8.11.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

The validation actions are automatically called (asynchronously of course) when the user is completing the register form :


Hope this helps image

Any question about this post? Feel free to drop a comment below or contact me on Twitter @jcorioland