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

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x000D   x000D   lt div class  text-danger  style  direction rtl  asp-validation-summary  All  gt  lt  div gt  x000D   x000D   x000D    simply use asp-validation-summary Tag Helper

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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   gt  v Errors                                                              Select  v   gt  v ErrorMessage         v Exception      or as an extension method  public static IEnumerable lt String gt  GetErrors this ModelStateDictionary modelState          return modelState Values SelectMany v   gt  v Errors                                 Select  v   gt  v ErrorMessage         v Exception  ToList

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Anybody looking for asp net core 3 1  Slightly updated than the above answer  I found that this is what  ApiController  returns  Dictionary lt string  List lt string gt  gt  errors   new Dictionary lt string  List lt string gt  gt                      foreach  KeyValuePair lt string  ModelStateEntry gt  kvp in ViewData ModelState                                        string key   kvp Key                      ModelStateEntry entry   kvp Value                       if  entry Errors Count  gt  0                                                List lt string gt  errorList   new List lt string gt                             foreach  ModelError error in entry Errors                                                        errorList Add error ErrorMessage                                                      errors key    errorList                                                           return  new JsonResult new  Errors   errors

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In case anyone wants to return the Name of the Model property for binding the error message in a strongly typed view   List lt ErrorResult gt  Errors   new List lt ErrorResult gt     foreach  KeyValuePair lt string  ModelState gt  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

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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

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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            lt summary gt          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          lt  summary gt           lt param name  modelState  gt modelState lt  param gt           lt returns gt  lt  returns gt      public static ModelError    It ModelStateDictionary modelState                var errors   modelState Values SelectMany x   gt  x Errors  ToArray            return errors

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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            lt summary gt          Returns a Key Value pair with all the errors in the model         according to the data annotation properties           lt  summary gt           lt param name  errDictionary  gt  lt  param gt           lt returns gt          Key  Name of the property         Value  The error message returned from data annotation          lt  returns gt      public static Dictionary lt string  string gt  GetModelErrors this ModelStateDictionary errDictionary                var errors   new Dictionary lt string  string gt             errDictionary Where k   gt  k Value Errors Count  gt  0  ForEach i   gt                        var er   string Join       i Value Errors Select e   gt  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   gt  errorsBuilder AppendFormat   0    1  -   key Key key Value            return errorsBuilder ToString

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During debugging I find it useful to put a table at the bottom of each of my pages to show all ModelState errors    lt table class  model-state  gt       foreach  var item in ViewContext ViewData ModelState                 if  item Value Errors Any                        lt tr gt               lt td gt  lt b gt  item Key lt  b gt  lt  td gt               lt td gt    item Value    null    item Value Value    null      lt null gt     item Value Value RawValue  lt  td gt               lt td gt   string Join       item Value Errors Select x   gt  x ErrorMessage    lt  td gt           lt  tr gt                   lt  table gt    lt style gt      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          lt  style gt

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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   gt  x Errors                                           Select x   gt  x ErrorMessage

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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  gt  0                   let val   state Value  AttemptedValue      NULL                      let errors   string Join      state Errors Select err   gt  err ErrorMessage                     select string Format   0    1    ERRORS   2     field  val  errors     Trace WriteLine string Join Environment NewLine  modelQuery

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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

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Useful for passing array of error messages to View  perhaps via Json   messageArray   this ViewData ModelState Values SelectMany modelState   gt  modelState Errors   modelState  error    gt  error ErrorMessage  ToArray

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Using LINQ   IEnumerable lt ModelError gt  allErrors   ModelState Values SelectMany v   gt  v Errors

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

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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

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I was able to do this using a little LINQ    public static List lt string gt  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

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var x   new Dictionary lt string string gt     for  var b   0  b  lt  ViewData ModelState Values Count    b          if  ViewData ModelState Values ElementAt b  Errors Count    gt  0          x Add ViewData ModelState Keys ElementAt b   String Join  quot   quot   ViewData              ModelState Values ElementAt b  Errors Select c   gt  c ErrorMessage

[asp.net-mvc] How to get all Errors from ASP.Net MVC modelState?

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