MVC 5 Html.ValidationSummary is not showing error - asp.net-mvc

Question

I am manually adding the following Model Error in my controller,
ModelState.AddModelError(string.Empty, "An error occurred");
However when the view is loaded, the #Html.ValidationSummary(true) is not showing any errors.
I have also tried #Html.ValidationSummary(false).
I have read many articles on this behavior and I have tried all the suggestions with no luck.
Any suggestions are greatly appreciated!

Answer 1

I can see it work. See the sample here: http://dotnetfiddle.net/Jz7wQj

Answer 2

Beware when using custom ViewData objects.
Problem Reproduced
Model
using System.ComponentModel.DataAnnotations;
namespace BrokenValidationSummaryTest.Models
{
public class MyModel
{
[Required]
public string Whatever { get; set; }
}
}
Controller
using BrokenValidationSummaryTest.Models;
using System.Web.Mvc;
namespace BrokenValidationSummaryTest.Controllers
{
public class HomeController : Controller
{
public ActionResult Index()
{
return View();
}
[HttpPost]
public ActionResult Submit(MyModel postedData)
{
return View(viewName: "Index", model: postedData);
}
}
}
View "Index"
#model BrokenValidationSummaryTest.Models.MyModel
<ul class="nav nav-tabs" id="carrier-tabs">
<li class="active">
<a data-toggle="tab" href="#search" class="tab-level-1" data-tab-name="search">Search</a>
</li>
</ul>
<div class="tab-content">
<div id="search" class="tab-pane fade in active">
#Html.Partial(partialViewName: "TabBody", model: Model, viewData: new ViewDataDictionary())
</div>
</div>
View "TabBody"
#model BrokenValidationSummaryTest.Models.MyModel
#Html.ValidationSummary(excludePropertyErrors: false)
<h2>TabBody</h2>
#using (Html.BeginForm(actionName: "Submit", controllerName: "Home", method: FormMethod.Post))
{
<div>Whatever:</div>
<div>#Html.TextBoxFor(x=>x.Whatever)</div>
<input type="submit" value="Submit">
}
Explanation
The partial view has the ValidationSummary HTML helper. We pass a custom ViewData object to the partial view. This custom ViewData object passed to the partial view does not contain the ViewState found in the view 'Index'. The HTML helper ValidationSummary does not have enough required information to render the error messages properly.
Recommendation: if using custom ViewData, populate the custom ViewData with the ViewState of the parent view.