ASP.NET MVC Updatemodel not updating but not throwing error

Question

Any ideas why this doesn't update but doesn't throw an error?

public ActionResult Edit(int id, [Bind(Exclude = "deptid")]FormCollection collection)
    {
        var department = _repository.ListOne(id); //Grabs record from linq to sql
        try
        {
            UpdateModel(department);
            _entities.SubmitChanges();

            // TODO: Add update logic here

            return RedirectToAction("Index");
        }
        catch
        {
            return View(department);
        }
    }

Answer 1

Sometimes what may happen is an error is thrown somewhere inside of the MVC assembly which is not handled nicely, and which does not get copied into your model state as expected. Then, when you try to display in your view the Html.ValidationSummary, it doesn't show you the error, which can be very confusing. One example that can crash this model binding process I've written about here. Usually, after you figure out why this is happening, you can make the corrections to your code and not worry about it anymore.

I have the following code that I use to inspect during debugging, to let me hover over it at a breakpoint and see what is really going on:

public static IDictionary<string, string> GetModelStateErrors(this ViewDataDictionary viewDataDictionary)
{
    Dictionary<string, string> dict = new Dictionary<string, string>();
    foreach (var modelStateKey in viewDataDictionary.ModelState.Keys)
    {
        var modelStateValue = viewDataDictionary.ModelState[modelStateKey];
        foreach (var error in modelStateValue.Errors)
        {
            var errorMessage = error.ErrorMessage;
            var exception = error.Exception;
            if (!String.IsNullOrEmpty(errorMessage))
            {
                dict.Add(modelStateKey, "Egads! A Model Error Message! " + errorMessage);
            }
            if (exception != null)
            {
                dict.Add(modelStateKey, "Egads! A Model Error Exception! " + exception.ToString());
            }
        }
    }
    return dict;
}

Then, I can insert this after I try to UpdateModel, and set a breakpoint on it:

var x = ViewData.GetModelStateErrors();

Put this right after your call to UpdateModel. Hovering over the x will show you any unhandled exceptions in the model-binding process, if that is what is really the problem here.

Good luck!