MaxJsonLength exception in ASP NET MVC during JavaScriptSerializer

Question

In one of my controller actions I am returning a very large JsonResult to fill a grid   I am getting the following InvalidOperationException exception   Error during serialization or deserialization using the JSON JavaScriptSerializer  The length of the string exceeds the value set on the maxJsonLength property   Setting the maxJsonLength property in the web config to a higher value unfortunately does not show any effect    lt system web extensions gt     lt scripting gt       lt webServices gt         lt jsonSerialization maxJsonLength  2147483644   gt       lt  webServices gt     lt  scripting gt   lt  system web extensions gt    I don t want to pass it back as a string as mentioned in this SO answer   In my research I came across this blog post where writing an own ActionResult  e g  LargeJsonResult   JsonResult  is recommended to bypass this behaviour   Is this then the only solution  Is this a bug in ASP NET MVC  Am I missing something   Any help would be most appreciated

User · Answer

I solved the issue by following this link  namespace System Web Mvc   public sealed class JsonDotNetValueProviderFactory   ValueProviderFactory       public override IValueProvider GetValueProvider ControllerContext controllerContext                if  controllerContext    null              throw new ArgumentNullException  controllerContext             if   controllerContext HttpContext Request ContentType StartsWith  application json   StringComparison OrdinalIgnoreCase               return null           var reader   new StreamReader controllerContext HttpContext Request InputStream           var bodyText   reader ReadToEnd             return String IsNullOrEmpty bodyText    null   new DictionaryValueProvider lt object gt  JsonConvert DeserializeObject lt ExpandoObject gt  bodyText  new ExpandoObjectConverter     CultureInfo CurrentCulture               protected void Application Start                 AreaRegistration RegisterAllAreas             RegisterGlobalFilters GlobalFilters Filters           RegisterRoutes RouteTable Routes              Remove and JsonValueProviderFactory and add JsonDotNetValueProviderFactory         ValueProviderFactories Factories Remove ValueProviderFactories Factories OfType lt JsonValueProviderFactory gt    FirstOrDefault             ValueProviderFactories Factories Add new JsonDotNetValueProviderFactory

User · Answer

there is a bit other case -  data is sent from client to server  when you are using controller method and model is huge         HttpPost      public ActionResult AddOrUpdateConsumerFile FileMetaDataModelView inputModel                if  inputModel    null  return null                    system throws exception like this  Error during serialization or deserialization using the JSON JavaScriptSerializer  The length of the string exceeds the value set on the maxJsonLength property  Parameter name  input   Only changing Web config settings is not enough to help in this case  You could additionally override mvc json serializer for supporting huge data model sizes or manually deserialize model from Request  Your controller method becomes       HttpPost      public ActionResult AddOrUpdateConsumerFile                 FileMetaDataModelView inputModel   RequestManager GetModelFromJsonRequest lt FileMetaDataModelView gt  HttpContext Request           if  inputModel    null  return null                           public static T GetModelFromJsonRequest lt T gt  HttpRequestBase request                string result               using  Stream req   request InputStream                        req Seek 0  System IO SeekOrigin Begin               result   new StreamReader req  ReadToEnd                      return JsonConvert DeserializeObject lt T gt  result

User · Answer

It appears this has been fixed in MVC4   You can do this  which worked well for me   public ActionResult SomeControllerAction       var jsonResult   Json veryLargeCollection  JsonRequestBehavior AllowGet     jsonResult MaxJsonLength   int MaxValue    return jsonResult

User · Answer

Unfortunately the web config setting is ignored by the default JsonResult implementation  So I guess you will need to implement a custom json result to overcome this issue

User · Answer

If use Json NET to generate the json string  it doesn t need to set MaxJsonLength value   return new ContentResult         Content   Newtonsoft Json JsonConvert SerializeObject data       ContentType    application json

User · Answer

this worked for me          JsonSerializerSettings json   new JsonSerializerSettings                       ReferenceLoopHandling   ReferenceLoopHandling Ignore                    var result   JsonConvert SerializeObject list  Formatting Indented  json           return new JsonResult   Data   result  MaxJsonLength   int MaxValue

User · Answer

I m surprised no one has suggested using a result filter  This is the cleanest way to globally hook into the action result pipeline   public class JsonResultFilter   IResultFilter       public int  MaxJsonLength   get  set         public int  RecursionLimit   get  set         public void OnResultExecuting ResultExecutingContext filterContext                if  filterContext Result is JsonResult jsonResult                           override properties only if they re not set             jsonResult MaxJsonLength   jsonResult MaxJsonLength    MaxJsonLength              jsonResult RecursionLimit   jsonResult RecursionLimit    RecursionLimit                       public void OnResultExecuted ResultExecutedContext filterContext                  Then  register an instance of that class using GlobalFilters Filters   GlobalFilters Filters Add new JsonResultFilter   MaxJsonLength   int MaxValue

User · Answer

protected override JsonResult Json object data  string contentType  System Text Encoding contentEncoding  JsonRequestBehavior behavior                return new JsonResult                         Data   data              ContentType   contentType              ContentEncoding   contentEncoding              JsonRequestBehavior   behavior              MaxJsonLength   Int32 MaxValue                    Was the fix for me in MVC 4

User · Answer

You could also use ContentResult as suggested here instead of subclassing JsonResult   var serializer   new JavaScriptSerializer   MaxJsonLength   Int32 MaxValue  RecursionLimit   100     return new ContentResult         Content   serializer Serialize data       ContentType    application json

User · Answer

Alternative ASP NET MVC 5 Fix   In my case the error was occurring during the request  Best approach in my scenario is modifying the actual JsonValueProviderFactory which applies the fix to the global project and can be done by editing the global cs file as such   JsonValueProviderConfig Config ValueProviderFactories Factories     add a web config entry    lt add key  aspnet MaxJsonLength  value  20971520    gt    and then create the two following classes  public class JsonValueProviderConfig       public static void Config ValueProviderFactoryCollection factories                var jsonProviderFactory   factories OfType lt JsonValueProviderFactory gt    Single            factories Remove jsonProviderFactory           factories Add new CustomJsonValueProviderFactory               This is basically an exact copy of the default implementation found in System Web Mvc but with the addition of a configurable web config appsetting value aspnet MaxJsonLength   public class CustomJsonValueProviderFactory   ValueProviderFactory             lt summary gt Returns a JSON value-provider object for the specified controller context  lt  summary gt           lt returns gt A JSON value-provider object for the specified controller context  lt  returns gt           lt param name  controllerContext  gt The controller context  lt  param gt      public override IValueProvider GetValueProvider ControllerContext controllerContext                if  controllerContext    null              throw new ArgumentNullException  controllerContext             object deserializedObject   CustomJsonValueProviderFactory GetDeserializedObject controllerContext           if  deserializedObject    null              return null           Dictionary lt string  object gt  strs   new Dictionary lt string  object gt  StringComparer OrdinalIgnoreCase           CustomJsonValueProviderFactory AddToBackingStore new CustomJsonValueProviderFactory EntryLimitedDictionary strs   string Empty  deserializedObject            return new DictionaryValueProvider lt object gt  strs  CultureInfo CurrentCulture              private static object GetDeserializedObject ControllerContext controllerContext                if   controllerContext HttpContext Request ContentType StartsWith  application json   StringComparison OrdinalIgnoreCase               return null           string fullStreamString    new StreamReader controllerContext HttpContext Request InputStream   ReadToEnd            if  string IsNullOrEmpty fullStreamString               return null           var serializer   new JavaScriptSerializer                         MaxJsonLength   CustomJsonValueProviderFactory GetMaxJsonLength                      return serializer DeserializeObject fullStreamString              private static void AddToBackingStore EntryLimitedDictionary backingStore  string prefix  object value                IDictionary lt string  object gt  strs   value as IDictionary lt string  object gt           if  strs    null                        foreach  KeyValuePair lt string  object gt  keyValuePair in strs                  CustomJsonValueProviderFactory AddToBackingStore backingStore  CustomJsonValueProviderFactory MakePropertyKey prefix  keyValuePair Key   keyValuePair Value                return                     IList lists   value as IList          if  lists    null                        backingStore Add prefix  value               return                     for  int i   0  i  lt  lists Count  i                          CustomJsonValueProviderFactory AddToBackingStore backingStore  CustomJsonValueProviderFactory MakeArrayKey prefix  i   lists i                         private class EntryLimitedDictionary               private static int  maximumDepth           private readonly IDictionary lt string  object gt   innerDictionary           private int  itemCount           static EntryLimitedDictionary                          maximumDepth   CustomJsonValueProviderFactory GetMaximumDepth                       public EntryLimitedDictionary IDictionary lt string  object gt  innerDictionary                        this  innerDictionary   innerDictionary                     public void Add string key  object value                        int num   this  itemCount   1              this  itemCount   num              if  num  gt   maximumDepth                                throw new InvalidOperationException  The length of the string exceeds the value set on the maxJsonLength property                               this  innerDictionary Add key  value                        private static string MakeArrayKey string prefix  int index                return string Concat prefix       index ToString CultureInfo InvariantCulture                    private static string MakePropertyKey string prefix  string propertyName                if  string IsNullOrEmpty prefix                         return propertyName                    return string Concat prefix       propertyName              private static int GetMaximumDepth                 int num          NameValueCollection appSettings   ConfigurationManager AppSettings          if  appSettings    null                        string   values   appSettings GetValues  aspnet MaxJsonDeserializerMembers                if  values    null  amp  amp  values Length    0  amp  amp  int TryParse values 0   out num                                 return num                                  return 1000             private static int GetMaxJsonLength                 int num          NameValueCollection appSettings   ConfigurationManager AppSettings          if  appSettings    null                        string   values   appSettings GetValues  aspnet MaxJsonLength                if  values    null  amp  amp  values Length    0  amp  amp  int TryParse values 0   out num                                 return num                                  return 1000

User · Answer

No need for a custom class  This is all that is needed   return new JsonResult   Data   Result  MaxJsonLength   Int32 MaxValue      where Result is that data you wish to serialize

User · Answer

You need to read from the configuration section manually before your code returns a JsonResult object  Simply read from web config in single line           var jsonResult   Json resultsForAjaxUI           jsonResult MaxJsonLength    ConfigurationManager GetSection  system web extensions scripting webServices jsonSerialization   as System Web Configuration ScriptingJsonSerializationSection  MaxJsonLength          return jsonResult    Be sure you defined configuration element in web config

User · Answer

You can try define in your LINQ expression only the field s that you will need   Example  Imagine that you have an Model with Id  Name  Phone and Picture  byte array  and need to load from json into an select list   LINQ Query   var listItems    from u in Users where u name Contains term  select u  ToList      The problem here is  select u  that get all fields  So  if you have big pictures  booomm   How to solve  very  very simple   var listItems    from u in Users where u name Contains term  select new  u Id  u Name   ToList      The best practices is select only the field that you will use   Remember  This is a simple tip  but can help many ASP NET MVC developpers

User · Answer

You can put this code in cshtml if you are returning view from controller and you want to increase the length of view bag data while encoding in json in cshtml             var jss   new System Web Script Serialization JavaScriptSerializer        jss MaxJsonLength   Int32 MaxValue      var userInfoJson   jss Serialize ViewBag ActionObj      var dataJsonOnActionGrid1    Html Raw userInfoJson     Now  dataJsonOnActionGrid1  will be accesible on js page and you will get proper result   Thanks

User · Answer

None of the above worked out for me until I changed the Action as  HttpPost    and made the ajax type as POST        HttpPost      public JsonResult GetSelectedSignalData string signal1                     JsonResult result   new JsonResult             var signalData   GetTheData             try                          var serializer   new System Web Script Serialization JavaScriptSerializer   MaxJsonLength   Int32 MaxValue  RecursionLimit   100                 result Data   serializer Serialize signalData               return Json result  JsonRequestBehavior AllowGet                                                          And the ajax call as    ajax       type   POST       url  some url      data  JSON stringify    signal1  signal1            contentType   application json  charset utf-8       success  function  data            if  data     null                setValue                          failure  function  data                errMessage   text  Error                  error  function  data                errMessage   text  Error

[asp.net-mvc] MaxJsonLength exception in ASP.NET MVC during JavaScriptSerializer

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