ASP.Net MVC 3 JSON Model Binding and server side model validation mixed with client side validation

Question

I\'ve been playing with the new MVC3 Json Model Binding and it\'s quite nice.

Currently, I can post JSON to controller and bind it. Model Validation occurs nicely too.

Answer 1

The following example works for me when using unobtrusive JavaScript in MVC3. I'm doing something very similar. Given the following JsonResponse class:

public enum Status
{
    Ok,
    Error
}

public class JsonResponse
{
    public Status Status { get; set; }
    public string Message { get; set; }
    public List Errors { get; set; }
}

My controller can have a method thus:

[HttpPost]
public ActionResult Login(UserLoginModel model)
{
    JsonResponse res = new JsonResponse();

    if (!ModelState.IsValid)
    {
        res.Status = Status.Error;
        res.Errors = GetModelStateErrorsAsString(this.ModelState);
        res.Message = "Oh dear, what have you done. Check the list of errors dude!";
    }
    else
    {
        // Save it here...

        // Return success
        res.Status = Status.Ok;
        res.Message = "Everything was hunky dory";
    }            

    return Json(res);
}

And the ModelStateDictionary can be enumerated for the errors as so:

private List GetModelStateErrorsAsString(ModelStateDictionary state)
{
    List errors = new List();

    foreach (var key in ModelState.Keys)
    {
        var error = ModelState[key].Errors.FirstOrDefault();
        if (error != null)
        {
            errors.Add(error.ErrorMessage);
        }
    }

    return errors;
}

Then in my view I can have the following JSON POST:

I'm using jQuery.tmpl to display the errors. I have excluded that from this example though.