JavaScriptSerializer - JSON serialization of enum as string

Question

I have a class that contains an enum property  and upon serializing the object using JavaScriptSerializer  my json result contains the integer value of the enumeration rather than its string  name    Is there a way to get the enum as a string in my json without having to create a custom JavaScriptConverter   Perhaps there s an attribute that I could decorate the enum definition  or object property  with   As an example   enum Gender   Male  Female    class Person       int Age   get  set        Gender Gender   get  set        Desired json result      Age   35   Gender    Male      Ideally looking for answer with built-in  NET framework classes  if not possible alternatives  like Json net  are welcome

User · Answer

You can actually use a JavaScriptConverter to accomplish this with the built-in JavaScriptSerializer. By converting your enum to a Uri you can encode it as a string.

I've described how to do this for dates but it can be used for enums as well. Custom DateTime JSON Format for .NET JavaScriptSerializer.

User · Answer

I have put together all of the pieces of this solution using the Newtonsoft Json library  It fixes the enum issue and also makes the error handling much better  and it works in IIS hosted services  It s quite a lot of code  so you can find it on GitHub here  https   github com jongrant wcfjsonserializer blob master NewtonsoftJsonFormatter cs  You have to add some entries to your Web config to get it to work  you can see an example file here  https   github com jongrant wcfjsonserializer blob master Web config

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I have found that Json NET provides the exact functionality I m looking for with a StringEnumConverter attribute   using Newtonsoft Json  using Newtonsoft Json Converters    JsonConverter typeof StringEnumConverter    public Gender Gender   get  set      More details at available on StringEnumConverter documentation   There are other places to configure this converter more globally     enum itself if you want enum always be serialized deserialized as string    JsonConverter typeof StringEnumConverter      enum Gender   Male  Female    In case anyone wants to avoid attribute decoration  you can add the converter to your JsonSerializer  suggested by Bj  rn Egil     serializer Converters Add new Newtonsoft Json Converters StringEnumConverter        and it will work for every enum it sees during that serialization  suggested by Travis    or JsonConverter  suggested by banana    JsonConvert SerializeObject MyObject       new Newtonsoft Json Converters StringEnumConverter        Additionally you can control casing and whether numbers are still accepted by using StringEnumConverter NamingStrategy  Boolean  constructor

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You can create JsonSerializerSettings with the call to JsonConverter SerializeObject as below   var result   JsonConvert SerializeObject                               dataObject                  new JsonSerializerSettings                                       Converters   new     new StringEnumConverter

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For  Net Core  -  public void ConfigureServices IServiceCollection services                services AddJsonFormatters f   gt  f Converters Add new StringEnumConverter

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Asp Net Core 3 with System Text Json  public void ConfigureServices IServiceCollection services         services          AddControllers            AddJsonOptions options   gt              options JsonSerializerOptions Converters Add new JsonStringEnumConverter

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Here is a simple solution that serializes a server-side C  enum to JSON and uses the result to populate a client-side  lt select gt  element  This works for both simple enums and bitflag enums   I have included the end-to-end solution because I think most people wanting to serialize a C  enum to JSON will also probably be using it to fill a  lt select gt  drop-down    Here goes   Example Enum  public enum Role       None   Permission None      Guest   Permission Browse      Reader   Permission Browse  Permission Help       Manager   Permission Browse   Permission Help   Permission Customise     A complex enum that uses bitwise ORs to generate a permissions system  So you can t rely on the simple index  0 1 2    for the integer value of the enum   Server Side - C   Get   roles         gt        var type   typeof Role       var data   Enum          GetNames type           Select name   gt  new                                Id    int Enum Parse type  name                    Name   name                          ToArray         return Response AsJson data        The code above uses the NancyFX framework to handle the Get request  It uses Nancy s Response AsJson   helper method - but don t worry  you can use any standard JSON formatter as the enum has already been projected into a simple anonymous type ready for serialization   Generated JSON          Id  0  Name   None          Id  2097155  Name   Guest          Id  2916367  Name   Reader          Id  4186095  Name   Manager       Client Side - CoffeeScript  fillSelect  id  url  selectedValue 0 - gt       select     id      option    item - gt      lt option  gt                           value    item Id               html    item Name               selected  selected  if item Id is selectedValue                 getJSON url  done  data - gt  option item  appendTo  select for item in data    - gt      fillSelect   role     roles   2916367   HTML Before   lt select id  role  name  role  gt  lt  select gt    HTML After   lt select id  role  name  role  gt       lt option value  0  gt None lt  option gt       lt option value  2097155  gt Guest lt  option gt       lt option value  2916367  selected  selected  gt Reader lt  option gt       lt option value  4186095  gt Manager lt  option gt   lt  select gt

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For ASP Net core Just add the following to your Startup Class   JsonConvert DefaultSettings         gt                        var settings   new JsonSerializerSettings                settings Converters Add new StringEnumConverter   AllowIntegerValues   false                 return settings

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In  net core 3 this is now possible with the built-in classes in System Text Json  edit  System Text Json is also available as a NuGet package for  net core 2 0 and  net framework 4 7 2 and later versions according to the docs   var person   new Person       Create and add a converter which will use the string representation instead of the numeric value  var stringEnumConverter   new System Text Json Serialization JsonStringEnumConverter    JsonSerializerOptions opts   new JsonSerializerOptions    opts Converters Add stringEnumConverter      Generate json string  var json   JsonSerializer Serialize lt Person gt  person  opts    To configure JsonStringEnumConverter with attribute decoration for the specific property  using System Text Json Serialization    JsonConverter typeof JsonStringEnumConverter    public Gender Gender   get  set     If you want to always convert the enum as string  put the attribute at the enum itself   JsonConverter typeof JsonStringEnumConverter     enum Gender   Male  Female

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You can also add a converter to your JsonSerializer if you don t want to use JsonConverter attribute   string SerializedResponse   JsonConvert SerializeObject       objToSerialize        new Newtonsoft Json Converters StringEnumConverter         It will work for every enum it sees during that serialization

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I wasn t able to change the source model like in the top answer  of  ob    and I didn t want to register it globally like  Iggy   So I combined https   stackoverflow com a 2870420 237091 and  Iggy s https   stackoverflow com a 18152942 237091 to allow setting up the string enum converter on during the SerializeObject command itself   Newtonsoft Json JsonConvert SerializeObject      objectToSerialize       Newtonsoft Json Formatting None       new Newtonsoft Json JsonSerializerSettings                 Converters   new List lt Newtonsoft Json JsonConverter gt                new Newtonsoft Json Converters StringEnumConverter

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Here is the answer for newtonsoft json  enum Gender   Male  Female    class Person       int Age   get  set          JsonConverter typeof StringEnumConverter        Gender Gender   get  set

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Person p   new Person            p Age   35          p Gender   Gender Male            1   male  Male           string male   Gender Male ToString             p Gender   Gender Female             2   female  Female           string female   Enum GetName typeof Gender   p Gender            JObject jobj   new JObject            jobj  Age     p Age          jobj  Gender     male          jobj  Gender2     female             you result   josn    Age   35  Gender    Male   Gender2    Female           string json   jobj ToString

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Add the below to your global asax for JSON serialization of c  enum as string    HttpConfiguration config   GlobalConfiguration Configuration              config Formatters JsonFormatter SerializerSettings Formatting                   Newtonsoft Json Formatting Indented               config Formatters JsonFormatter SerializerSettings Converters Add                  new Newtonsoft Json Converters StringEnumConverter

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And for VB net I found the following works   Dim sec   New Newtonsoft Json Converters StringEnumConverter   sec NamingStrategy     New Serialization CamelCaseNamingStrategy  Dim JSON s As New JsonSerializer JSON s Converters Add sec   Dim jsonObject As JObject jsonObject   JObject FromObject SomeObject  JSON s  Dim text   jsonObject ToString  IO File WriteAllText filePath  text

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This version of Stephen s answer doesn t change the name in the JSON    DataContract      Namespace            http   schemas datacontract org 2004 07 Whatever    class Person        DataMember      int Age   get  set         Gender Gender   get  set          DataMember Name    Gender        string GenderString               get   return this Gender ToString              set                         Gender g               this Gender   Enum TryParse value  true  out g    g   Gender Male

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This is an old question but I thought I d contribute just in case  In my projects I use separate models for any Json requests  A model would typically have same name as domain object with  Json  prefix  Models are mapped using AutoMapper  By having the json model declare a string property that is an enum on domain class  AutoMapper will resolve to it s string presentation   In case you are wondering  I need separate models for Json serialized classes because inbuilt serializer comes up with circular references otherwise   Hope this helps someone

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new JavaScriptSerializer   Serialize         from p        in  new List lt Person gt                new Person                             Age   35                Gender   Gender Male                            select new   Age  p Age  Gender p Gender ToString             ToArray   0

User · Answer

This is easily done by adding a ScriptIgnore attribute to the Gender property  causing it to not be serialised  and adding a GenderString property which does get serialised   class Person       int Age   get  set          ScriptIgnore      Gender Gender   get  set         string GenderString   get   return Gender ToString

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Just in case anybody finds the above insufficient  I ended up settling with this overload   JsonConvert SerializeObject objToSerialize  Formatting Indented  new Newtonsoft Json Converters StringEnumConverter

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A slightly more future-proof option  Facing the same question  we determined that we needed a custom version of StringEnumConverter to make sure that our enum values could expand over time without breaking catastrophically on the deserializing side  see background below   Using the SafeEnumConverter below allows deserialization to finish even if the payload contains a value for the enum that does not have a named definition  closer to how int-to-enum conversion would work   Usage    SafeEnumConverter  public enum Colors       Red      Green      Blue      Unsupported   -1     or   SafeEnumConverter  int  Colors Blue   public enum Colors       Red      Green      Blue     Source   public class SafeEnumConverter   StringEnumConverter       private readonly int  defaultValue       public SafeEnumConverter                    if you ve been careful to  always  create enums with  0  reserved            as an unknown default value  which you should   you could use 0 here            defaultValue   -1             public SafeEnumConverter int defaultValue                 defaultValue   defaultValue                  lt summary gt          Reads the provided JSON and attempts to convert using StringEnumConverter  If that fails set the value to the default value           lt  summary gt           lt returns gt The deserialized value of the enum if it exists or the default value if it does not  lt  returns gt      public override object ReadJson JsonReader reader  Type objectType  object existingValue  JsonSerializer serializer                try                       return base ReadJson reader  objectType  existingValue  serializer                     catch                       return Enum Parse objectType      defaultValue                          public override bool CanConvert Type objectType                return base CanConvert objectType   amp  amp  objectType GetTypeInfo   IsEnum            Background  When we looked at using the StringEnumConverter  the problem we had is that we also needed passivity for cases when a new enum value was added  but not every client was immediately aware of the new value  In these cases  the StringEnumConverter packaged with Newtonsoft JSON throws a JsonSerializationException similar to  Error converting value SomeString to type EnumType  and then the whole deserialization process fails  This was a deal breaker for us  because even if the client planned on ignoring discarding the property value that it didn t understand  it still needed to be capable of deserializing the rest of the payload

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ASP NET Core way   public class Startup     public IServiceProvider ConfigureServices IServiceCollection services          services AddMvc   AddJsonOptions options   gt              options SerializerSettings Converters Add new Newtonsoft Json Converters StringEnumConverter                     https   gist github com regisdiogo 27f62ef83a804668eb0d9d0f63989e3e

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Noticed that there is no answer for serialization when there is a Description attribute   Here is my implementation that supports the Description attribute   public class CustomStringEnumConverter   Newtonsoft Json Converters StringEnumConverter       public override void WriteJson JsonWriter writer  object value  JsonSerializer serializer                Type type   value GetType   as Type           if   type IsEnum  throw new InvalidOperationException  Only type Enum is supported            foreach  var field in type GetFields                          if  field Name    value ToString                                  var attribute   Attribute GetCustomAttribute field  typeof DescriptionAttribute   as DescriptionAttribute                  writer WriteValue attribute    null   attribute Description   field Name                    return                                   throw new ArgumentException  Enum not found              Enum    public enum FooEnum          Will be serialized as  Not Applicable       Description  Not Applicable        NotApplicable          Will be serialized as  Applicable      Applicable     Usage    JsonConverter typeof CustomStringEnumConverter    public FooEnum test   get  set

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Not sure if this is still relevant but I had to write straight to a json file and I came up with the following piecing several stackoverflow answers together  public class LowercaseJsonSerializer       private static readonly JsonSerializerSettings Settings   new JsonSerializerSettings               ContractResolver   new LowercaseContractResolver               public static void Serialize TextWriter file  object o                JsonSerializer serializer   new JsonSerializer                         ContractResolver   new LowercaseContractResolver                Formatting   Formatting Indented              NullValueHandling   NullValueHandling Ignore                    serializer Converters Add new Newtonsoft Json Converters StringEnumConverter             serializer Serialize file  o              public class LowercaseContractResolver   DefaultContractResolver               protected override string ResolvePropertyName string propertyName                        return Char ToLowerInvariant propertyName 0     propertyName Substring 1                       It assures all my json keys are lowercase starting according to json  rules    Formats it cleanly indented and ignores nulls in the output   Aslo by adding a StringEnumConverter it prints enums with their string value   Personally I find this the cleanest I could come up with  without having to dirty the model with annotations   usage       internal void SaveJson string fileName                   serialize JSON directly to a file         using  StreamWriter file   File CreateText  fileName                         LowercaseJsonSerializer Serialize file  jsonobject

User · Answer

No there is no special attribute you can use  JavaScriptSerializer serializes enums to their numeric values and not their string representation  You would need to use custom serialization to serialize the enum as its name instead of numeric value     If you can use JSON Net instead of JavaScriptSerializer than see  answer on this question provided by OmerBakhari  JSON net covers this use case  via the attribute  JsonConverter typeof StringEnumConverter     and many others not handled by the built in  net serializers  Here is a link comparing features and functionalities of the serializers

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The combination of Omer Bokhari and uri  s answers is alsways my solution since the values that I want to provide is usually different from what I have in my enum specially that I would like to be able to change my enums if I need to   So if anyone is interested  it is something like this   public enum Gender       EnumMember Value    male        Male      EnumMember Value    female        Female    class Person       int Age   get  set         JsonConverter typeof StringEnumConverter        Gender Gender   get  set

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Iggy answer sets JSON serialization of c  enum as string only for ASP NET  Web API and so    But to make it work also with ad hoc serialization  add following to your start class  like Global asax Application Start     convert Enums to Strings  instead of Integer  globally JsonConvert DefaultSettings         gt        var settings   new JsonSerializerSettings        settings Converters Add new StringEnumConverter   CamelCaseText   true         return settings        More information on the Json NET page  Additionally  to have your enum member to serialize deserialize to from specific text  use the      System Runtime Serialization EnumMember   attribute  like this   public enum time zone enum        EnumMember Value    Europe London         EuropeLondon        EnumMember Value    US Alaska         USAlaska

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