C# .NET MVC3 ModelState.IsValid

Question

Im using JSON to post data from a form and ModelState.isValid() returning false, i put a WriteLine for all incoming data and everything looks fine data wise, is there a way to display model state errors to figure out what is not validating? this exact code works fine with other models

[HttpPost]
public ActionResult mobileCreateAction(Trip trip)
{
    if (ModelState.IsValid)
    {
        System.Diagnostics.Debug.WriteLine("saving");
        DB.Trips.Add(trip);
        DB.SaveChanges();
        return Json(new
        {
            success = true,
            msg = "Success saving trip"
        });
    }
    else
    {
        System.Diagnostics.Debug.WriteLine("invalid model state");
        return Json(new
        {
            success = false,
            msg = "Error saving trip"
        }, JsonRequestBehavior.AllowGet);
    }  
}

thanks

score 34 · Accepted Answer · answered Apr 01 '11 at 08:32

34

To get a list of errors in the model state:

var errors = ModelState
    .Where(x => x.Value.Errors.Count > 0)
    .Select(x => new { x.Key, x.Value.Errors })
    .ToArray();

Then put a break point on this line and inspect the errors variable. It will give you a list of properties on your model with their respective errors.

answered Apr 01 '11 at 08:32

Darin Dimitrov

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Darin when i print errors im getting this value: <>f__AnonymousType1`2[System.String,System.Web.Mvc.ModelErrorCollection], any idea what it means? – z.eljayyo Apr 03 '11 at 23:06
That line outputs an array of anonymous objects with two properties (Key and Errors). Try accessing those properties ans print that. – Megacan Jul 18 '12 at 12:15

score 2 · Answer 2 · answered Apr 01 '11 at 08:41

You can find the errors in the ModelState.Values collection. Every value has an Errors collection that contains all the model errors for that property.

var errors = from v in ModelState.Values 
             where v.Errors.Count > 0 
             select v.Errors;

score 0 · Answer 3 · edited May 23 '17 at 10:33

SO Post

Building on @Darin's answer the post linked above provides the code needed to display the 'why' message.

 foreach (var obj in ModelState.Values)
            {
                foreach (var error in obj.Errors)
                {
                    if (!string.IsNullOrEmpty(error.ErrorMessage))
                        System.Diagnostics.Debug.WriteLine("ERROR WHY = " + error.ErrorMessage);
                }
            }

C# .NET MVC3 ModelState.IsValid

3 Answers3

Linked