Serialize enum to string

I have an enum:

public enum Action {
    Remove=1,
    Add=2
}

And a class:

[DataContract]
public class Container {
    [DataMember]
    public Action Action {get; set;}
}

When serialize instance of Container to json I get: {Action:1} (in case Action is Remove).

I would like to get: {Action:Remove} (instead of int I need to ToString form of the enum)

Can I do it without adding another member to the class?

Using Json.Net, you can define a custom StringEnumConverter as

public class MyStringEnumConverter : Newtonsoft.Json.Converters.StringEnumConverter
{
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        if (value is Action)
        {
            writer.WriteValue(Enum.GetName(typeof(Action),(Action)value));// or something else
            return;
        }

        base.WriteJson(writer, value, serializer);
    }
}

and serialize as

string json=JsonConvert.SerializeObject(container,new MyStringEnumConverter());

You can just add the attribute:

    [Newtonsoft.Json.JsonConverter(typeof(StringEnumConverter))] 

to the enum property that is not serializing as a string.

or if you have a more exotic formattting in mind you could use the attributes as below to tell the JSON serializer to serialise only the property that you have formatted as you wish. Depends a bit on the rest of your implementation. It recognises the DataMember attribute on a property as well.

[JsonObject(MemberSerialization = MemberSerialization.OptOut)]
public class Container
{
    public Action Action { get; set; }

    [JsonProperty(PropertyName = "Action")]
    public string ActionString
    {
        get
        {
            return Action.ToString();
        }
    }
}

The JSON formatter has very specialized behaviour when working with enumerations; the normal Data Contract attributes are ignored and it treats your enum as a number, not the more human-readable string you'd expect with other formats. Whilst this makes it easy to deal with flag-type enumerations, it makes most other types much harder to work with.

From MSDN:

Enumeration member values are treated as numbers in JSON, which is different from how they are treated in data contracts, where they are included as member names. For more information about the data contract treatment, see Enumeration Types in Data Contracts.

• For example, if you have public enum Color {red, green, blue, yellow, pink}, serializing yellow produces the number 3 and not the string "yellow".

• All enum members are serializable. The EnumMemberAttribute and the NonSerializedAttribute attributes are ignored if used.

• It is possible to deserialize a nonexistent enum value - for example, the value 87 can be deserialized into the previous Color enum even though there is no corresponding color name defined.

• A flags enum is not special and is treated the same as any other enum.

The only practical way to resolve this, to allow end-users to specify a string instead of a number, is to not use the enum in your contract. Instead the practical answer is to replace your enum with a string and perform internal validation on the value such that it can be parsed into one of the valid enum representations.

Alternatively (though not for the feint of heart), you could replace the JSON formatter with your own, which would respect enumerations in the same way as other formatters.

Here's a simple way to do this:

JsonConvert.SerializeObject(myObject, Formatting.Indented, new StringEnumConverter());

I've been using a very good workaround by using an auxiliary private property for serialization and deserialization that works either for serialization by the enum member name or by the value of the EnumMemberAttribute.

The greatest advantages I see, are that:

• You don't need to tweak with the serializer
• All the serialization logic is contained in the Data Object
• You can hide your auxiliary property by setting it's accessibility modifier to private, since the DataContractSerializers are able to get and set private properties
• You are able to serialize the enum as a string instead of an int

Your class will look like this:

[DataContract]
public class SerializableClass {
    public Shapes Shape {get; set;} //Do not use the DataMemberAttribute in the public property

    [DataMember(Name = "shape")]
    private string ShapeSerialization // Notice the PRIVATE here!
    {
        get { return EnumHelper.Serialize(this.Shape); }
        set { this.Shape = EnumHelper.Deserialize<Shapes>(value); }
    }
}

EnumHelper.cs

/* Available at: https://gist.github.com/mniak/a4d09264ad1ca40c489178325b98935b */
public static class EnumHelper
{
    public static string Serialize<TEnum>(TEnum value)
    {
        var fallback = Enum.GetName(typeof(TEnum), value);
        var member = typeof(TEnum).GetMember(value.ToString()).FirstOrDefault();
        if (member == null)
            return fallback;
        var enumMemberAttributes = member.GetCustomAttributes(typeof(EnumMemberAttribute), false).Cast<EnumMemberAttribute>().FirstOrDefault();
        if (enumMemberAttributes == null)
            return fallback;
        return enumMemberAttributes.Value;
    }
    public static TEnum Deserialize<TEnum>(string value) where TEnum : struct
    {
        TEnum parsed;
        if (Enum.TryParse<TEnum>(value, out parsed))
            return parsed;

        var found = typeof(TEnum).GetMembers()
            .Select(x => new
            {
                Member = x,
                Attribute = x.GetCustomAttributes(typeof(EnumMemberAttribute), false).OfType<EnumMemberAttribute>().FirstOrDefault()
            })
            .FirstOrDefault(x => x.Attribute?.Value == value);
        if (found != null)
            return (TEnum)Enum.Parse(typeof(TEnum), found.Member.Name);
        return default(TEnum);
    }
}