Errors

public List<string> GetModelStateErrors(ModelStateDictionary ModelState)
    {
        List<string> errorMessages = new List<string>();

        var validationErrors = ModelState.Values.Select(x => x.Errors);
        validationErrors.ToList().ForEach(ve => {
            var errorStrings = ve.Select(x => x.ErrorMessage);
            errorStrings.ToList().ForEach(em => {
                errorMessages.Add(em);
            });
        });

        return errorMessages;
    }

 if (!ModelState.IsValid)

        {
            return Json(new { success = false, errors = GetModelStateErrors(ModelState) }, JsonRequestBehavior.AllowGet);
        }

function displayValidationErrors(errors)
{
    var $ul = $('div.validation-summary-valid.text-danger > ul');

    $ul.empty();
    $.each(errors, function (idx, errorMessage) {
        $ul.append('<li>' + errorMessage + '</li>');
    });
}

That's how we handle it via ajax:

$.ajax({
    cache: false,
    async: true,
    type: "POST",
    url: form.attr('action'),
    data: form.serialize(),
    success: function (data) {
        var isSuccessful = (data['success']);

        if (isSuccessful) {
            $('#partial-container-steps').html(data['view']);
            initializePage();
        }
        else {
            var errors = data['errors'];

            displayValidationErrors(errors);
        }
    }
});

Render partial views via ajax in the following way:
var view = this.RenderRazorViewToString(partialUrl, viewModel);
        return Json(new { success = true, view }, JsonRequestBehavior.AllowGet);
 
 

public string RenderRazorViewToString(string viewName, object model)
    {
        ViewData.Model = model;
        using (var sw = new StringWriter())
        {
            var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext,
                                                                     viewName);
            var viewContext = new ViewContext(ControllerContext, viewResult.View,
                                         ViewData, TempData, sw);
            viewResult.View.Render(viewContext, sw);
            viewResult.ViewEngine.ReleaseView(ControllerContext, viewResult.View);
            return sw.GetStringBuilder().ToString();
        }
    }

Simple line to return errors

return ModelState.Values.SelectMany(x => x.Errors).Select(x => x.ErrorMessage).ToList();

up vote down vote

You can do it this way: (Edit: Considering that you're waiting for a response json with dataType: 'json') .NET public JsonResult Edit(EditPostViewModel data) { if(ModelState.IsValid) { // Save return Json(new { Ok = true } ); } return Json(new { Ok = false } ); } JS: success: function (data) { if (data.Ok) { alert('success'); } else { alert('problem'); } },