An RX IObservable Extension method to Merge two streams together based on a Key

RX_Observable_JoinMerge.cs

  public static class ObsExt
  {
    // Taken from this example here: 
    // http://rxwiki.wikidot.com/101samples#toc39
    public static IObservable<TResult> JoinMerge<TOuter, TInner, TKey, TResult>
      (this IObservable<TOuter> outer_,
       IObservable<TInner> inner_,
       Func<TOuter, TKey> outerKeySelector_,
       Func<TInner, TKey> innerKeySelector_,
       Func<TOuter, TInner, TResult> resultSelector_)
    {
      var joinedStream =
        outer_.GroupJoin(inner_,
          _ => Observable.Never<TOuter>(),
          _ => Observable.Never<TInner>(),
          (ou_, in_) => new { Outer = ou_, Inner = in_ });

      return Observable.Create<TResult>(obs_ =>
      {
        IDisposable innerSubscription = 
          joinedStream.Subscribe(inOut_ => inOut_.Inner
            .Where(x_ => innerKeySelector_(x_).Equals(outerKeySelector_(inOut_.Outer)))
            .Subscribe(merged_ =>
              obs_.OnNext(resultSelector_(inOut_.Outer, merged_))));

        return innerSubscription.Dispose;
      });
    }
  }

Looks like a bug with the Dispose.
It should dispose both the joinedStream and the innerSubscription.