C# 5.0 in a Nutshell, 5th Edition

Chapter 14. Concurrency & Asynchrony

Most applications need to deal with more than one thing happening at a time (concurrency). In this chapter, we start with the essential prerequisites, namely the basics of threading and tasks, and then describe the principles of asynchrony and C# 5.0’s asynchronous functions in detail.

In Chapter 22, we’ll revisit multithreading in greater detail, and in Chapter 23, we’ll cover the related topic of parallel programming.

Introduction

The most common concurrency scenarios are:

Writing a responsive user interface

In WPF, Metro, and Windows Forms applications, you must run time-consuming tasks concurrently with the code that runs your user interface to maintain responsiveness.

Allowing requests to process simultaneously

On a server, client requests can arrive concurrently and so must be handled in parallel to maintain scalability. If you use ASP.NET, WCF, or Web Services, the .NET Framework does this for you automatically. However, you still need to be aware of shared state (for instance, the effect of using static variables for caching.)

Parallel programming

Code that performs intensive calculations can execute faster on multicore/multiprocessor computers if the workload is divided between cores (Chapter 23 is dedicated to this).

Speculative execution

On multicore machines, you can sometimes improve performance by predicting something that might need to be done, and then doing it ahead of time. LINQPad uses this technique to speed up the creation of new queries. ...