[Rx]Extensions for tagging an event stream. Useful for when you need to combine two observables and can't use anonymous types

ObservableMixins.cs

    public static class ObservableMixins
    {
        public static IObservable<ObjectTag<T, V>> Tag<T, V>(this IObservable<V> sequenceToTag, T tag)
        {
            return sequenceToTag.Tag(_ => tag);
        }

        public static IObservable<ObjectTag<T, V>> Tag<T, V>(this IObservable<V> sequenceToTag, Func<V, T> tagFunction)
        {
            return sequenceToTag.Select(v => new ObjectTag<T, V>(tagFunction(v), v));
        }
    }

    public class ObjectTag<T, J>
    {
        public T Tag { get; private set; }
        public J Value { get; private set; }

        public ObjectTag(T tag, J val)
        {
            Tag = tag;
            Value = val;
        }
    }