How to get all Errors from ASP.Net MVC modelState?

Question

I want to get all the error messages out of the modelState without knowing the key values. Looping through to grab all the error messages that the ModelState contains.

How can I do this?

Answer 1

Using LINQ:

IEnumerable<ModelError> allErrors = ModelState.Values.SelectMany(v => v.Errors);

Answer 2

foreach (ModelState modelState in ViewData.ModelState.Values) {
    foreach (ModelError error in modelState.Errors) {
        DoSomethingWith(error);
    }
}

See also How do I get the collection of Model State Errors in ASP.NET MVC?.

Answer 3

Building on the LINQ verison, if you want to join all the error messages into one string:

string messages = string.Join("; ", ModelState.Values
                                        .SelectMany(x => x.Errors)
                                        .Select(x => x.ErrorMessage));

Answer 4

I was able to do this using a little LINQ,

public static List<string> GetErrorListFromModelState
                                              (ModelStateDictionary modelState)
{
      var query = from state in modelState.Values
                  from error in state.Errors
                  select error.ErrorMessage;

      var errorList = query.ToList();
      return errorList;
}

The above method returns a list of validation errors.

Further Reading :

How to read all errors from ModelState in ASP.NET MVC

Answer 5

During debugging I find it useful to put a table at the bottom of each of my pages to show all ModelState errors.

<table class="model-state">
    @foreach (var item in ViewContext.ViewData.ModelState) 
    {
        if (item.Value.Errors.Any())
        { 
        <tr>
            <td><b>@item.Key</b></td>
            <td>@((item.Value == null || item.Value.Value == null) ? "<null>" : item.Value.Value.RawValue)</td>
            <td>@(string.Join("; ", item.Value.Errors.Select(x => x.ErrorMessage)))</td>
        </tr>
        }
    }
</table>

<style>
    table.model-state
    {
        border-color: #600;
        border-width: 0 0 1px 1px;
        border-style: solid;
        border-collapse: collapse;
        font-size: .8em;
        font-family: arial;
    }

    table.model-state td
    {
        border-color: #600;
        border-width: 1px 1px 0 0;
        border-style: solid;
        margin: 0;
        padding: .25em .75em;
        background-color: #FFC;
    }
 </style>

Answer 6

As I discovered having followed the advice in the answers given so far, you can get exceptions occuring without error messages being set, so to catch all problems you really need to get both the ErrorMessage and the Exception.

String messages = String.Join(Environment.NewLine, ModelState.Values.SelectMany(v => v.Errors)
                                                           .Select( v => v.ErrorMessage + " " + v.Exception));

or as an extension method

public static IEnumerable<String> GetErrors(this ModelStateDictionary modelState)
{
      return modelState.Values.SelectMany(v => v.Errors)
                              .Select( v => v.ErrorMessage + " " + v.Exception).ToList();

}

Answer 7

In case anyone wants to return the Name of the Model property for binding the error message in a strongly typed view.

List<ErrorResult> Errors = new List<ErrorResult>();
foreach (KeyValuePair<string, ModelState> modelStateDD in ViewData.ModelState)
{
    string key = modelStateDD.Key;
    ModelState modelState = modelStateDD.Value;

    foreach (ModelError error in modelState.Errors)
    {
        ErrorResult er = new ErrorResult();
        er.ErrorMessage = error.ErrorMessage;
        er.Field = key;
        Errors.Add(er);
    }
}

This way you can actually tie the error in with the field that threw the error.

Answer 8

Outputting just the Error messages themselves wasn't sufficient for me, but this did the trick.

var modelQuery = (from kvp in ModelState
                  let field = kvp.Key
                  let state = kvp.Value
                  where state.Errors.Count > 0
                  let val = state.Value?.AttemptedValue ?? "[NULL]"

                  let errors = string.Join(";", state.Errors.Select(err => err.ErrorMessage))
                  select string.Format("{0}:[{1}] (ERRORS: {2})", field, val, errors));

Trace.WriteLine(string.Join(Environment.NewLine, modelQuery));

Answer 9

For just in case someone need it i made and use the following static class in my projects

Usage example:

if (!ModelState.IsValid)
{
    var errors = ModelState.GetModelErrors();
    return Json(new { errors });
}

Usings:

using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.Mvc;
using WebGrease.Css.Extensions;

Class:

public static class ModelStateErrorHandler
{
    /// <summary>
    /// Returns a Key/Value pair with all the errors in the model
    /// according to the data annotation properties.
    /// </summary>
    /// <param name="errDictionary"></param>
    /// <returns>
    /// Key: Name of the property
    /// Value: The error message returned from data annotation
    /// </returns>
    public static Dictionary<string, string> GetModelErrors(this ModelStateDictionary errDictionary)
    {
        var errors = new Dictionary<string, string>();
        errDictionary.Where(k => k.Value.Errors.Count > 0).ForEach(i =>
        {
            var er = string.Join(", ", i.Value.Errors.Select(e => e.ErrorMessage).ToArray());
            errors.Add(i.Key, er);
        });
        return errors;
    }

    public static string StringifyModelErrors(this ModelStateDictionary errDictionary)
    {
        var errorsBuilder = new StringBuilder();
        var errors = errDictionary.GetModelErrors();
        errors.ForEach(key => errorsBuilder.AppendFormat("{0}: {1} -", key.Key,key.Value));
        return errorsBuilder.ToString();
    }
}

Answer 10

And this works too:

var query = from state in ModelState.Values
    from error in state.Errors
    select error.ErrorMessage;
var errors = query.ToArray(); // ToList() and so on...

Answer 11

Anybody looking for asp.net core 3.1. Slightly updated than the above answer. I found that this is what [ApiController] returns

 Dictionary<string, List<string>> errors = new Dictionary<string, List<string>>();

                foreach (KeyValuePair<string, ModelStateEntry> kvp in ViewData.ModelState)
                {
                    string key = kvp.Key;
                    ModelStateEntry entry = kvp.Value;

                    if (entry.Errors.Count > 0)
                    {
                        List<string> errorList = new List<string>();
                        foreach (ModelError error in entry.Errors)
                        {
                            errorList.Add(error.ErrorMessage);
                        }

                        errors[key] = errorList;
                    }
                }

                return  new JsonResult(new {Errors = errors});