How to tell Json.Net globally to apply the StringEnumConverter to all enums

Add a StringEnumConverter to the JsonSerializerSettings Converters collection.

Documentation: Serialize with JsonConverters

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If you want the serializer to use camelCasing, you can set this as well:

SerializerSettings.Converters.Add(
    new StringEnumConverter { CamelCaseText = true });

This will serialize SomeValue to someValue.

The other answers work for ASP.NET, but if you want to set these settings generally for calling JsonConvert in any context you can do:

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

(See http://james.newtonking.com/archive/2013/05/08/json-net-5-0-release-5-defaultsettings-and-extension-data)

In your Global.asax.cs add

HttpConfiguration config = GlobalConfiguration.Configuration;
config.Formatters.JsonFormatter.SerializerSettings.Converters.Add
                (new Newtonsoft.Json.Converters.StringEnumConverter());