Asynchronous actions with RX

I was trying to come up with a syntactically tidy way to run some code in the ThreadPool.

Assume I have a function as follows that performs the work:

void PopulateIsolatedStorageList()
{
    using (iso = IsolatedStorageFile.GetUserStoreForApplication())
    {
        string[] found = iso.ISO.GetDirectoryNames("Logs/*.*");
        foreach (string s in found)
        {
            // do some time consuming processing here
        }
    }
}

First I attempted to create an Action delegate for the above, and then tried to do this:

Action b = this.PopulateIsolatedStorageList;
Observable.FromAsyncPattern(b.BeginInvoke, b.EndInvoke    )().
    ObserveOn(Scheduler.ThreadPool).Subscribe();

This did not work.  First, PopulateIsolatedStorageList ended up with a null this pointer.

Secondly, it seemed to run on the main thread in any case.

A bit of lateral thinking required

What are my goals?

1. I want to run my action on a worker thread.


2. I want to perform some completed action on the UI thread (namely OnPropertyChanged).

Why not create an enumeration of things I want to get done on the worker thread then?

Action[] a = { PopulateIsolatedStorageList};
a.ToObservable(Scheduler.ThreadPool).Subscribe
    ( action => action(), 
      () => Deployment.Current.Dispatcher.BeginInvoke(() => UINotify() ));

Where UINotify() is the expression to perform on the main thread.

 

And surprisingly, it all works.

Update – It helps if you find the right method

Having searched some more I found another mechanism, which removes the need to create the array, and is probably the proper way to do it.

Observable.ToAsync(PopulateIsolatedStorageList)()
    .Subscribe(
     _ => { },
     () => Deployment.Current.Dispatcher.BeginInvoke(() => UINotify() ));