Multithreaded .NET Web service clients: threads and responsiveness

VB.NET Tutorial: Unresponsive programs are extremely frustrating to use. Applications that sometimes freeze for a moment are a source of much irritation, especially if they don't provide any feedback on what they are doing, or how long it is likely to be before they start responding again.

---

by Ian Griffiths and Chris Sells, consultants. Intel Corp.

Unresponsive programs are extremely frustrating to use. Applications that sometimes freeze for a moment are a source of much irritation, especially if they don't provide any feedback on what they are doing, or how long it is likely to be before they start responding again. This behaviour can be particularly common among applications that use remote facilities such as Web services. This article describes how to maintain responsiveness in .NET Windows Forms rich client applications, even when invoking potentially long-running Web services, by using multiple threads.

Multithreaded programs are notoriously hard to write. The number of ways in which different parts of a program can interact can grow exponentially when we move from sequential, single-threaded operation to concurrent execution. This makes it extremely hard to understand the program's execution, and if we don't understand that, how can we ever be sure that our implementation is correct? So when contemplating writing a multithreaded program, we need compelling answers to two questions: what will the benefits of multithreaded execution be, and how can we manage the complexity?