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?

Luckily

If you're just displaying the errors, then @Html.ValidationSummary() is a quick way to display them all in razor. – Kimberelykimberlee

foreach (var error in ViewData.ModelState.Values.SelectMany(modelState => modelState.Errors)) { DoSomething(error); } – Pash

Thanks everyone for pointing me in the right direction. Like @viggity said, Keys are important and this did it for me: ModelState.Where(e=>e.Value.Errors.Count > 0).ToList() – Dreamland

A side note: If you debug just ModelState variable, you can see some interesting information. – Arnulfoarny

answer for a similar question https://mcmap.net/q/74747/-get-error-message-if-modelstate-isvalid-fails – Poteat

@Dreamland the answer that includes key is below from Jivan Bhandari https://mcmap.net/q/73551/-how-to-get-all-errors-from-asp-net-mvc-modelstate – Trillbee

Answer 1

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?.

Coo

Very helpful. Note in some scenarios, such as binding failures and bad requests, there will be ModelState entries with empty string for Value.ErrorMessage and instead a Value.Exception.Message – Danczyk

Errors are nice but sometimes you want the key of the modelstate too (i.e. the name of the field). you can get that by changing the first line to this: foreach (KeyValuePair<string, ModelState> kvp in htmlHelper.ViewData.ModelState) { and insert this line below it: var modelState = kvp.Value;. You can get the key from kvp.Key – Psychosis

@viggity, the answer that includes key is below from Jivan Bhandari https://mcmap.net/q/73551/-how-to-get-all-errors-from-asp-net-mvc-modelstate – Trillbee

Answer 2

Using LINQ:

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

Cartilaginous

Modified to return IEnumerable<string> with just the error message:: var allErrors = ModelState.Values.SelectMany(v => v.Errors.Select(b => b.ErrorMessage)); – Birt

This is great, but unfortunately Watch/Immediate windows don't support lambda's :( – Danczyk

Does not work for me. Values does not contain a definition for Select many. Do I have to include anything, any library, LINQ or something? – Legge

Yes! I (you, anyone) needs "using System.Linq;" in the top. Otherwise you got the message 'Values does not contain a definition for Select many'. It was missing in my case. – Legge

@Danczyk Visual Studio 2015 does. – Konstanz

@HakamFostok why in the hell not? – Shaunta

@HakamFostok If you are typing out all of your variable types instead of using var, you are wasting your time. – Greengrocer

@DaveVandenEynde because one thing "Readability" – Judiciary

@Greengrocer typing out all of variable types will save the person's time who read our code, so it is saving time. – Judiciary

@hakam-fostok @jb06 you're both right. Typing List<string> errors = new List<string>() instead of var errors = new List<string>() is realy a waste of time, but writing IEnumerable<ModelError> allErrors = ModelState.Values.SelectMany(v => v.Errors);, where the return type is not really clear, is really greater in term of readability. (even if visual studio can give it to you on mouse hover) – Finicky

I was using this, until I encountered a: modified enumeration operation may not execute Error This isn't safe if used with a foreach() that subsequently appends a message to the ModelStateDictionary (for validation error output in view), and additionally doesn't handle the situation where the message is empty but the Exception object is not. This is certainly not a valid solution, it just looks pretty. – Stab

Some things like ModelState.Values.SelectMany(v => v.Errors).ToList()[0] can be easy to peek the error – Mestizo

It's worth noting that you may need to look at Exception rather than ErrorMessage. – Genitals

ModelState.Values do not include keys, that are important to understand errors. the answer that includes key is below from Jivan Bhandari https://mcmap.net/q/73551/-how-to-get-all-errors-from-asp-net-mvc-modelstate – Trillbee

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));

Greenlet

The other option is to do the following: ModelState.Values.SelectMany(x => x.Errors).Select(x => x.ErrorMessage).JoinString("; "); – Peppery

@Tod, is IEnumerable.JoinString() your own extension method? See https://mcmap.net/q/74749/-c-how-to-join-a-list-with-delim-e-g-list-lt-string-gt-strlist-then-strlist-join-quot-quot/188926 – Greenlet

Hey Dunc - yes I suspect I have added that extension method to my code base and have forgotten about it and then thought it was a framework method LOL :( – Peppery

or ... ModelState.Values.SelectMany(O => O.Errors).Select(O => O.ErrorMessage).Aggregate((U, V) => U + ", " + V) – Barnacle

you can also do the select on the errors :) Not sure if it matters: ModelState.Values.SelectMany(x => x.Errors.Select(x => x.ErrorMessage)) – Casey

This works great when you are using web api and returning an IHttpActionResult result. So, you can just do: return BadRequest(messages); Thanks, Dunc! – Disbranch

How would also add the Key name? I would assume this is the name of the input control that was missing or failed IsValid. – Collins

@Collins With Key name: ModelState.SelectMany(x => x.Value.Errors.Select(y => $"{x.Key}: {y.ErrorMessage}")) – Greenlet

Thanks Dunc! I came up with this: string messages = string.Join(Environment.NewLine, ModelState .SelectMany(x => x.Value.Errors.Select(y => $"{x.Key}: {y.ErrorMessage}"))); Boy, that syntax makes my eyes cross. I am very grateful. – Collins

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

Magog

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>

Rodomontade

if there's any edge cases here where this fails please just edit the answer to fix it – Rodomontade

Thank you for this, it helped me solve an issue that I possibly could not figure out. – Underwriter

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();

}

Menashem

why would you want a string with all the errors in it? doesn't make sense when you want to do something with it in the view, an array of list is way better imho – Chrischrism

To debug. My first problem was to find out what was going wrong with my app. I wasn't trying to tell the user just find out what was going wrong. Besides it's trivial to convert that example from creating an enumeration of strings to an enumeration of something else, e.g. error message and exception so the really useful thing is knowing that you need both bits of information – Menashem

BTW you did realise the second extension method returns IEnumerable<String> and not just a big single string? – Menashem

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.

Blakey

Answer 8

This code snippet is useful too and give you a List that contains of Error Messges.

var errors = ModelState.Values.SelectMany(x => x.Errors.Select(c => c.ErrorMessage)).ToList();

Pauperism

Answer 9

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));

Winglet

As a warning, the key value pairs in ModelState may include NULL values, which is why the original code here included some cute C# 6 business with a null-coalesce operator (?.), hence the currying to the ?? at the end of the expression. The original expression which should protect from null errors was: state.Value.?AttemptedValue ?? "[NULL]". As far as I know, the code in its current state, without the sneaky handling of cases where state.Value == null, is at risk. – Winglet

Answer 10

Anybody looking for asp.net core 3.1. The answer includes key (field name). Most of other answers include only errors.

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});

Parthenope

Answer 11

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();
    }
}

Submarine

Thanks CodeArtist !! I made a small change in the code below its implementation . – Carabiniere

Answer 12

<div class="text-danger" style="direction:rtl" asp-validation-summary="All"></div>

simply use asp-validation-summary Tag Helper

Jab

Answer 13

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...

Symposiac

@Yasser Have you seen Toto's answer? – Calends

@TheMuffinMan yes I have. What about it ? – Magog

@Yasser It's the best answer. Nothing wrong with this one, but no point in using it when SelectMany is available. – Calends

Answer 14

Useful for passing array of error messages to View, perhaps via Json:

messageArray = this.ViewData.ModelState.Values.SelectMany(modelState => modelState.Errors, (modelState, error) => error.ErrorMessage).ToArray();

Afteryears

Answer 15

This is expanding upon the answer from @Dunc . See xml doc comments

// ReSharper disable CheckNamespace
using System.Linq;
using System.Web.Mvc;


public static class Debugg
{
    /// <summary>
    /// This class is for debugging ModelState errors either in the quick watch 
    /// window or the immediate window.
    /// When the model state contains dozens and dozens of properties, 
    /// it is impossible to inspect why a model state is invalid.
    /// This method will pull up the errors
    /// </summary>
    /// <param name="modelState">modelState</param>
    /// <returns></returns>
    public static ModelError[]  It(ModelStateDictionary modelState)
    {
        var errors = modelState.Values.SelectMany(x => x.Errors).ToArray();
        return errors;            
    }
}

Kailey

Answer 16

For AJAX Request better solution:

    public IActionResult Demo(DemoInfo formData)
    {
        if (!ModelState.IsValid)
        {
            IEnumerable<object> formErrors = ModelState.Select((s) => new { 
                fieldName = s.Key, 
                fieldValue = s.Value.RawValue,
                fieldMessage = s.Value.Errors.FirstOrDefault()?.ErrorMessage
            });
            return Json(new { formValid = 0, formErrors });
        }
        return Json(new { formValid = 1 });
    }

Response format will be:

{"formValid":0,
 "formErrors":[{
     "fieldName":"name of field from object",
     "fieldValue":"value from browser",
     "fieldMessage":null /*Error message from model annotations if field is valid the value will be null */
 }]
}

For more details about Func<> check this page : Func<TSource,Int32,TResult>)

Taperecord

Answer 17

In addition, ModelState.Values.ErrorMessage may be empty, but ModelState.Values.Exception.Message may indicate an error.

Chicane

Answer 18

var x = new Dictionary<string,string>();
for (var b = 0; b < ViewData.ModelState.Values.Count(); b++)
{
    if (ViewData.ModelState.Values.ElementAt(b).Errors.Count() > 0)
        x.Add(ViewData.ModelState.Keys.ElementAt(b), String.Join(",", ViewData
            .ModelState.Values.ElementAt(b).Errors.Select(c => c.ErrorMessage)));
}

Grew

@GuilhermeSilva is a contributor – Grew

Answer 19

get error with Field Name and Error Message

var errors = new List<ErrorDto>();
foreach (KeyValuePair<string, ModelStateEntry> kvp in context.ModelState)
{
    if (kvp.Value.Errors.Count > 0)
    {
        errors.Add(new ErrorDto()
        {
            FieldName = kvp.Key,
            ErrorMessage = string.Join(",", kvp.Value.Errors.Select(v => v.ErrorMessage))
        });
    }
}

Error Model

    public class ErrorDto
    {
        public string FieldName { get; set; }
        public string ErrorMessage { get; set; }
    }

Sundew

Answer 20

In your implementation you are missing static Class, this should be.

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

rather

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

Carabiniere

Answer 21

var result = string.Join(',',ModelState.Values.SelectMany(v => v.Errors).Select(a=>a.ErrorMessage));

Christogram