Convert nested c#-type to json and use it in javascript

I have a C# class as container for constant values used by the application.

public abstract class MyConstants
{
    public abstract class HttpMethods
    {
        public const string Put = "PUT";
        public const string Post = "POST";
        public const string Get = "GET";
    }

    public abstract class ContainerKeys
    {
        public abstract class GlobalModal
        {
            public const string DialogId = "6698CB2F-2948-45D9-8902-2C13A7ED6335";
        }
    }

    public const int MaximumImageUploadSize = 3 * 1024 * 1024; // 3MB
    public const int MaximumDocumentUploadSize = 5 * 1024 * 1024; // 5MB
}

How can this be converted to a json which can then be copied inside to a javascript-file to use it like MyConstants.HttpMethods.Put inside javascript?

Using

var constants = typeof(MyConstants).GetFields().ToDictionary(x => x.Name, x => x.GetValue(null));
var json = new JavaScriptSerializer().Serialize(constants);
return JavaScript(json + ";");

only returns {"MaximumImageUploadSize":3145728,"MaximumDocumentUploadSize":5242880}; without all the nested classes/constants.

The question seems more related to use reflection on a Type with muliple nested other Types.