Although I agree that JavaScriptSerializer is a crap and Json.Net is a better option, there is a way in which you can make JavaScriptSerializer serialize the way you want to.
You will have to register a converter and override the Serialize method using something like this:

    public class KeyValuePairJsonConverter : JavaScriptConverter

{

    public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)

    {

        var instance = Activator.CreateInstance(type);



        foreach (var p in instance.GetType().GetPublicProperties())

        {

            instance.GetType().GetProperty(p.Name).SetValue(instance, dictionary[p.Name], null);

            dictionary.Remove(p.Name);

        }



        foreach (var item in dictionary)

            (instance).Add(item.Key, item.Value);



        return instance;

    }

    public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)

    {

        var result = new Dictionary<string, object>();

        var dictionary = obj as IDictionary<string, object>;

        foreach (var item in dictionary)

            result.Add(item.Key, item.Value);

        return result;

    }

    public override IEnumerable<Type> SupportedTypes

    {

        get

        {

            return new ReadOnlyCollection<Type>(new Type[] { typeof(your_type) });

        }

    }

}



JavaScriptSerializer javaScriptSerializer = new JavaScriptSerializer();

javaScriptSerializer.RegisterConverters(new JavaScriptConverter[] { new ExpandoJsonConverter() });

jsonOfTest = javaScriptSerializer.Serialize(test);

// {x:xvalue,y:/Date(1314108923000)/}

Hope this helps!