gistfile1.cs

//
// Get the webpage and block till it finishes (aka make an async func
// into a sync func)
//

string contents = GetWebpageAsStringAsync("http://foo").First();

// ...or wire up a callback

GetWebpageAsStringAsync("http://foo").Subscribe(x => {
    Console.WriteLine(x);
});

//
// Get all three pages concurrently and retrieve the results
// as they come in
//

string[] pages = new[] { "http://foo", "http://bar", "http://baz" };

IObservable<string> websiteContent = pages.AsObservable().SelectMany(GetWebpageAsStringAsync);

websiteContent.Subscribe(x => {
    Console.WriteLine(x);
});

//
// How about we get fancy, and do a running word count of all the pages
// we've looked at.
//

IObservable<int> runningTotal = pages.AsObservable()
    .SelectMany(GetWebpageAsStringAsync)
    .Scan(0, (acc, x) => acc + x.Split(" ").Length)

runningTotal.Subscribe(x => Console.WriteLine("Words we've seen so far: {0}", x));

//
// Ok, now let's mash the two together to get a running *average* words
// per site
//

IObservable<double> average = Observable.Zip(
    websiteContent.Count(),
    runningTotal,
    (siteCount, totalWords) => (double)totalWords / siteCount);

average.Subscribe(x => Console.WriteLine("Average Words per Site: {0}", x));