CODEWITHSUNDEEP
c#asp.netasp.net-mvc
Steven
Steven

Reputation: 18859

Get error message if ModelState.IsValid fails?

I have this function in my controller.

[HttpPost]
public ActionResult Edit(EmployeesViewModel viewModel)
{
    Employee employee = GetEmployee(viewModel.EmployeeId);
    TryUpdateModel(employee);

    if (ModelState.IsValid)
    {
        SaveEmployee(employee);
        TempData["message"] = "Employee has been saved.";
        return RedirectToAction("Details", new { id = employee.EmployeeID });
    }

    return View(viewModel); // validation error, so redisplay same view
}

It keeps failing, ModelState.IsValid keeps returning false and redisplaying the view. But I have no idea what the error is.

Is there a way to get the error and redisplay it to the user?

Upvotes: 111

Views: 204667

Answers (14)

Zuel
Zuel

Reputation: 41

I like creating a ModelState extension method

public static class ModelStateExtensions
{

    public static BadRequestObjectResult As<BadRequestObjectResult>(this ModelStateDictionary modelState) 
    {
        var message = string.Join("\r\n", modelState.Values
                                           .SelectMany(v => v.Errors)
                                           .Select(e => e.ErrorMessage));
        return (BadRequestObjectResult)Activator.CreateInstance(typeof(BadRequestObjectResult), message)!;
    }
}

Then use it like

        if (!ModelState.IsValid)
        {
            return ModelState.As<BadRequestObjectResult>();
        }

Upvotes: 2

Ali
Ali

Reputation: 1200

i use this method as a generic way to get errors

 public static List<string> GetModelErrros(ModelStateDictionary modelState)
        {
            var errors = modelState.Values.Where(E => E.Errors.Count > 0)
                         .SelectMany(E => E.Errors)
                         .Select(E => E.ErrorMessage)
                         .ToList();

            return errors;
        }

and you may use it

logger.LogInformation("ID {0} input Error  ", string.Join(",", SiteUtils.GetModelErrros(ModelState)));

Upvotes: 3

paulsm4
paulsm4

Reputation: 121649

Here's a useful snippet I can copy/paste into my OnPostASync() handler to quickly identify the failing validation item(s):

public async Task<IActionResult> OnPostAsync(string editButton)
    {
        if (!ModelState.IsValid)
        {
            var errors = 
                from value in ModelState.Values
                where value.ValidationState == ModelValidationState.Invalid
                select value;  
            return Page();  // <-- I set a breakpoint here, and examine "errors"
        }
        ...

Unlike some of the other solutions above, I can see both

  1. The error message text (ErrorMessage) ... AND ...
  2. The specific field that caused the error

Upvotes: 5

San Jaisy
San Jaisy

Reputation: 17078

publicIHttpActionResultPost(Productproduct) {  
    if (ModelState.IsValid) {  
        //Dosomethingwiththeproduct(notshown).  
        returnOk();  
    } else {  
        returnBadRequest();  
    }  
}

OR

public HttpResponseMessage Post(Product product)
        {
            if (ModelState.IsValid)
            {
                // Do something with the product (not shown).

                return new HttpResponseMessage(HttpStatusCode.OK);
            }
            else
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }

Upvotes: 0

user781861
user781861

Reputation: 89

ModelState.Values.SelectMany(v => v.Errors).ToList().ForEach(x => _logger.Error($"{x.ErrorMessage}\n"));

Upvotes: 3

Captain Kenpachi
Captain Kenpachi

Reputation: 7215

Try this

if (ModelState.IsValid)
{
    //go on as normal
}
else
{
    var errors = ModelState.Select(x => x.Value.Errors)
                           .Where(y=>y.Count>0)
                           .ToList();
}

errors will be a list of all the errors.

If you want to display the errors to the user, all you have to do is return the model to the view and if you haven't removed the Razor @Html.ValidationFor() expressions, it will show up.

if (ModelState.IsValid)
{
    //go on as normal
}
else
{
    return View(model);
}

The view will show any validation errors next to each field and/or in the ValidationSummary if it's present.

Upvotes: 179

codeMonkey
codeMonkey

Reputation: 4815

If anyone is here for WebApi (not MVC) you just return the ModelState object:

return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);

Upvotes: 6

Delmirio Segura
Delmirio Segura

Reputation: 1691

Try

ModelState.Values.First().Errors[0].ErrorMessage

Upvotes: -1

OMANSAK
OMANSAK

Reputation: 1332

It is sample extension

public class GetModelErrors
{
    //Usage return Json to View :
    //return Json(new { state = false, message = new GetModelErrors(ModelState).MessagesWithKeys() });
    public class KeyMessages
    {
        public string Key { get; set; }
        public string Message { get; set; }
    }
    private readonly ModelStateDictionary _entry;
    public GetModelErrors(ModelStateDictionary entry)
    {
        _entry = entry;
    }

    public int Count()
    {
        return _entry.ErrorCount;
    }
    public string Exceptions(string sp = "\n")
    {
        return string.Join(sp, _entry.Values
            .SelectMany(v => v.Errors)
            .Select(e => e.Exception));
    }
    public string Messages(string sp = "\n")
    {
        string msg = string.Empty;
        foreach (var item in _entry)
        {
            if (item.Value.ValidationState == ModelValidationState.Invalid)
            {
                msg += string.Join(sp, string.Join(",", item.Value.Errors.Select(i => i.ErrorMessage)));
            }
        }
        return msg;
    }

    public List<KeyMessages> MessagesWithKeys(string sp = "<p> ● ")
    {
        List<KeyMessages> list = new List<KeyMessages>();
        foreach (var item in _entry)
        {
            if (item.Value.ValidationState == ModelValidationState.Invalid)
            {
                list.Add(new KeyMessages
                {
                    Key = item.Key,
                    Message = string.Join(null, item.Value.Errors.Select(i => sp + i.ErrorMessage))
                });
            }
        }
        return list;
    }
}

Upvotes: 3

Mostafa Basha
Mostafa Basha

Reputation: 45

Ok Check and Add to Watch:

  1. Do a breakpoint at your ModelState line in your Code
  2. Add your model state to your Watch
  3. Expand ModelState "Values"
  4. Expand Values "Results View"

Now you can see a list of all SubKey with its validation state at end of value.

So search for the Invalid value.

Upvotes: 2

JohnnyHK
JohnnyHK

Reputation: 311865

If you're looking to generate a single error message string that contains the ModelState error messages you can use SelectMany to flatten the errors into a single list:

if (!ModelState.IsValid)
{
    var message = string.Join(" | ", ModelState.Values
        .SelectMany(v => v.Errors)
        .Select(e => e.ErrorMessage));
    return new HttpStatusCodeResult(HttpStatusCode.BadRequest, message);
}

Upvotes: 115

Sachin T Sawant
Sachin T Sawant

Reputation: 759

If Modal State is not Valid & the error cannot be seen on screen because your control is in collapsed accordion, then you can return the HttpStatusCode so that the actual error message is shown if you do F12. Also you can log this error to ELMAH error log. Below is the code

if (!ModelState.IsValid)
{
              var message = string.Join(" | ", ModelState.Values
                                            .SelectMany(v => v.Errors)
                                            .Select(e => e.ErrorMessage));

                //Log This exception to ELMAH:
                Exception exception = new Exception(message.ToString());
                Elmah.ErrorSignal.FromCurrentContext().Raise(exception);

                //Return Status Code:
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest, message);
}

But please note that this code will log all validation errors. So this should be used only when such situation arises where you cannot see the errors on screen.

Upvotes: 9

user1056921
user1056921

Reputation: 31

I have no idea if this is your problem, but if you add a user and then change the name of your application, that user will remain in the database (of course), but will be invalid (which is correct behavior). However, there will be no error added for this type of failure. The error list is empty, but ModelState.IsValid will return false for the login.

Upvotes: -1

Daniel Schaffer
Daniel Schaffer

Reputation: 57832

You can do this in your view without doing anything special in your action by using Html.ValidationSummary() to show all error messages, or Html.ValidationMessageFor() to show a message for a specific property of the model.

If you still need to see the errors from within your action or controller, see the ModelState.Errors property

Upvotes: 43

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