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.

Answer 1

I have found that Json.NET provides the exact functionality I'm looking for with a JsonConverter attribute, passing in the built-in StringEnumConverter type:

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 Bjørn 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.

Answer 2

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 Omer Bokhari: 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.

Answer 3

@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 = (() =>
{
    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
}

Answer 4

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());

Answer 5

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<Person>(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 }

Answer 6

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<Newtonsoft.Json.JsonConverter> {
            new Newtonsoft.Json.Converters.StringEnumConverter()
        }
    })

Answer 7

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; }
}

Answer 8

ASP.NET Core way:

public class Startup
{
  public IServiceProvider ConfigureServices(IServiceCollection services)
  {
    services.AddMvc().AddJsonOptions(options =>
    {
      options.SerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter());
    });
  }
}

https://gist.github.com/regisdiogo/27f62ef83a804668eb0d9d0f63989e3e

Answer 9

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(); } }
}

Answer 10

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; 
        }
    }
}

Answer 11

Here is the answer for newtonsoft.json

enum Gender { Male, Female }

class Person
{
    int Age { get; set; }

    [JsonConverter(typeof(StringEnumConverter))]
    Gender Gender { get; set; }
}

Answer 12

Asp.Net Core 3 with System.Text.Json

public void ConfigureServices(IServiceCollection services)
{

    services
        .AddControllers()
        .AddJsonOptions(options => 
           options.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter())
        );

    //...
 }

Answer 13

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.

Answer 14

For .NET 6.0 if you want to use the built-in JsonSerializer (System.Text.Json)

Then, it comes out-of-the-box, you just need to use the built-in JsonStringEnumConverter attribute. For example:

[JsonConverter(typeof(JsonStringEnumConverter))]
public SomeEnumType EnumProperty { get; set; }

And that's it, BUT make sure your SomeEnumType contains values with the exact string values, otherwise it will throw an exception. Casing seems to be insensitive.

Reference: https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-customize-properties?pivots=dotnet-6-0#enums-as-strings

Answer 15

Here is a simple solution that serializes a server-side C# enum to JSON and uses the result to populate a client-side <select> 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 <select> 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"] = _ =>
{
    var type = typeof(Role);
    var data = Enum
        .GetNames(type)
        .Select(name => 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)->
    $select = $ id
    $option = (item)-> $ "<option/>", 
        {
            value:"#{item.Id}"
            html:"#{item.Name}"
            selected:"selected" if item.Id is selectedValue
        }
    $.getJSON(url).done (data)->$option(item).appendTo $select for item in data

$ ->
    fillSelect "#role", "/roles", 2916367

HTML Before

<select id="role" name="role"></select>

HTML After

<select id="role" name="role">
    <option value="0">None</option>
    <option value="2097155">Guest</option>
    <option value="2916367" selected="selected">Reader</option>
    <option value="4186095">Manager</option>
</select>

Answer 16

For ASP.Net core Just add the following to your Startup Class:

JsonConvert.DefaultSettings = (() =>
        {
            var settings = new JsonSerializerSettings();
            settings.Converters.Add(new StringEnumConverter { AllowIntegerValues = false });
            return settings;
        });

Answer 17

You can create JsonSerializerSettings with the call to JsonConverter.SerializeObject as below:

var result = JsonConvert.SerializeObject
            (
                dataObject,
                new JsonSerializerSettings
                {
                    Converters = new [] {new StringEnumConverter()}
                }
            );

Answer 18

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; }

Answer 19

For .Net Core :-

public void ConfigureServices(IServiceCollection services)
{
    ...
    services.AddJsonFormatters(f => f.Converters.Add(new StringEnumConverter()));
    ...
}

Answer 20

Use this:

using Newtonsoft.Json;
using Newtonsoft.Json.Converters;

[Serializable]
[JsonConverter(typeof(StringEnumConverter))]
public enum Gender { Male, Female }

Answer 21

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())

Answer 22

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.

Answer 23

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.

Answer 24

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;
    }

    /// <summary>
    /// Reads the provided JSON and attempts to convert using StringEnumConverter. If that fails set the value to the default value.
    /// </summary>
    /// <returns>The deserialized value of the enum if it exists or the default value if it does not.</returns>
    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) && 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!

Answer 25

The namespace System.Text.Json.Serialization has JsonStringEnumConverter which can be used like below. [JsonConverter(typeof(JsonStringEnumConverter))]

Answer 26

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);
        }
    }

Answer 27

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)

Answer 28

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

Answer 29

For anyone needing a solution in May of '22 for .NET 6 and still using Newtonsoft, you can register the converter globally like this:

var builder = WebApplication.CreateBuilder(args);
...
builder.Services.AddControllers(options => options.RespectBrowserAcceptHeader = true)
.AddNewtonsoftJson(opt =>
{
    opt.SerializerSettings.ContractResolver = new DefaultContractResolver();
    opt.SerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter());
})
.AddXmlSerializerFormatters()
.AddXmlDataContractSerializerFormatters();

Answer 30

        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();

Answer 31

new JavaScriptSerializer().Serialize(  
    (from p   
    in (new List<Person>() {  
        new Person()  
        {  
            Age = 35,  
            Gender = Gender.Male  
        }  
    })  
    select new { Age =p.Age, Gender=p.Gender.ToString() }  
    ).ToArray()[0]  
);