The Visual Studio Async CTP combines a new simple and composable pattern for asynchronous APIs, with "await" and "async" language keywords in Visual Basic and C#, that avoids asynchronous code having to be written "inside-out" using callbacks. The CTP is a painless install/uninstall on top of Visual Studio 2010 RTM, and comes with plenty of samples and documentation. The single AsyncCtpLibrary assembly is just 104Kb, and the Silverlight version only 132Kb. Recommended, because it's pretty likely you'll see this in C# 5. Multiple logical flow are really simple to implement now. No extra threads running, but you can implement them customly.