How can I 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?

• levininja: If you're just displaying the errors, then @Html.ValidationSummary() is a quick way to display them all in razor.
• Razvan Dumitru: foreach (var error in ViewData.ModelState.Values.SelectMany(modelState => modelState.Errors)) { DoSomething(error); }
• user3590235: 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()
• carloswm85: A side note: If you debug just ModelState variable, you can see some interesting information.
• Ali: answer for a similar question stackoverflow.com/a/68022337/6741585

Answer 1

Using LINQ:

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

• Kieran: Modified to return IEnumerable<string> with just the error message:: var allErrors = ModelState.Values.SelectMany(v => v.Errors.Select(b => b.ErrorMessage))
• AaronLS: This is great, but unfortunately Watch/Immediate windows don't support lambda's :(
• Estevez: 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.
• Hakan Fıstık: @JB06 typing out all of variable types will save the person's time who read our code, so it is saving time.
• aprovent: @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)

Answer 2

Use:

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? .

• AaronLS: 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
• viggity: 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
• Michael Freidgeim: @viggity, the answer that includes key is below from Jivan Bhandari stackoverflow.com/a/65676216/52277

Answer 3

Building on the LINQ version, 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));

• Tod Thomson: The other option is to do the following: ModelState.Values.SelectMany(x => x.Errors).Select(x => x.ErrorMessage).JoinString("; ")
• Dunc: @Tod, is IEnumerable.JoinString() your own extension method? See stackoverflow.com/q/4382034/188926
• Tod Thomson: 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 :(
• fordareh: or ... ModelState.Values.SelectMany(O => O.Errors).Select(O => O.ErrorMessage).Aggregate((U, V) => U + ", " + V)
• Rich Ward: This works great when you are using web api and returning an IHttpActionResult result. So, you can just do: return BadRequest(messages); Thanks, Dunc!

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 occurring 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();
}

• Daniël Tulp: 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
• Alan Macdonald: 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
• Alan Macdonald: BTW you did realise the second extension method returns IEnumerable<String> and not just a big single string?

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

This code snippet is useful too and gives you a List<string> that contains the error messages.

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

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));

• Josh Sutterfield: 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.

Answer 10

If anybody is 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});

Answer 11

For just in case someone needs it, I made and used the following static class in my projects.

Usage example:

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

Usage:

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 12

Use:

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

Simply use the asp-validation-summary tag helper:

<div class="text-danger" asp-validation-summary="All">
</div>

Answer 13

For an Ajax request, a better solution is:

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 });
}

The response format will be:

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

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

Answer 14

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 15

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

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

Answer 16

This is expanding upon the answer from Dunc. See the XML document 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;
 }
}

Answer 17

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

Answer 18

Get the error with a 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; }
}

Answer 19

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)));
}

• Peter Mortensen: "Explanation is vital for a good answer."

Answer 20

With fieldName...

if (!this.ModelState.IsValid)
{
 foreach (var modelState in this.ModelState)
 {
 foreach (var error in modelState.Value.Errors)
 {
 rModel.AddError(error.ErrorMessage, ErrorType.Error, modelState.Key);
 }
 }
 rModel.Message = "Invalid Data";
 return false;
}

• Peter Mortensen: "Explanation is vital for a good answer." . Thanks in advance.

Answer 21

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 });
}

Answer 22

Use:

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

• Peter Mortensen: "Explanation is vital for a good answer."