ASP.NET MVC 2 server-side validation for ajax form

Question

I've faced the following problem. I'm developing a form for the site and this form should have validation. I wanna to use native ASP.NET MVC 2 validation functionality but get stubborn with it. I have a form that is loaded via $.get and displayed using jQuery UI modal dialog. All examples I found explains how to use MVC validation with simple forms and avoid Ajax forms.

I can enable client side validation for this form, but I need to handle server-side validation correctly. How can I handle server-side validation model errors for ajax forms?

Answer 1

When you pass your object back to the controller, you have to wrap your code in If ModelState.IsValid

Below is a simplified version of how I edit a user. The first "EDIT" sends the User object TO the View. The second "EDIT" handles the post from the view.

Function Edit() As ActionResult
    ''# do stuff to populate your User
    Return View(User)
End Function

<AcceptVerbs(HttpVerbs.Post)> _
Function Edit(ByVal user as User)
    If ModelState.IsValid Then
        ''# do your valid stuff
    Else
        ''# The posted form was not valid, send the user back
        Return View(user)
    End If
End Function

Here's the same thing in C#

public ActionResult Edit()
{
    // do stuff to populate your User
    return View(User);
}

[AcceptVerbs(HttpVerbs.Post)]
public object Edit(User user)
{
    if (ModelState.IsValid) {
            // do your valid stuff
    } else {
        //'# The posted form was not valid, send the user back
        return View(user);
    }
}

EDIT:

On your view, if you want to add AJAX validation, just add the following.

    <% 
        Html.EnableClientValidation() ''# This is where all the magic happens.  It will build your clientside validation for you out of your MetaData.
        Using Html.BeginForm("Edit", "Users")
    %>

      <!-- all your markup crap -->
            <tr>
                <td>
                    <%: Html.LabelFor(Function(model) model.UserName)%></td>
                <td>
                    <%: Html.TextBoxFor(Function(model) model.UserName) %>
                    <%: Html.ValidationMessage("UserName", "*")%><br />
                </td>
            </tr>

      <!-- somewhere you'll want to add a Validation Summary of all your errors -->
      <%= Html.ValidationSummary("Oops!, please correct the errors...") %>


      <% End Using%>
      <!-- bottom of the page -->

          <script src="../../Assets/Scripts/MicrosoftAjax.js" type="text/javascript"></script>
          <script src="../../Assets/Scripts/MicrosoftMvcAjax.js" type="text/javascript"></script>
          <script src="../../Assets/Scripts/MicrosoftMvcValidation.js" type="text/javascript"></script>

EDIT:

Here is some info on rendering using Ajax.BeginForm
http://singulartechnologies.com/asp-net-mvc-ajax-beginform-sample-code
http://msdn.microsoft.com/en-us/library/dd381533.aspx
http://weblogs.asp.net/mikebosch/archive/2008/02/15/asp-net-mvc-submitting-ajax-form-with-jquery.aspx