Professional C# and .NET, 2021st Edition

11Tasks and Asynchronous Programming

WHAT'S IN THIS CHAPTER?

• The importance of asynchronous programming
• Using the async and await keywords with the task-based async pattern
• Creating and using tasks
• Foundations of asynchronous programming
• Error handling with asynchronous methods
• Cancellation of asynchronous methods
• Async streams
• Asynchronous programming with Windows apps

CODE DOWNLOADS FOR THIS CHAPTER

The source code for this chapter is available on the book page at www.wiley.com. Click the Downloads link. The code can also be found at https://github.com/ProfessionalCSharp/ProfessionalCSharp2021 in the directory 1_CS/Tasks.

The code for this chapter is divided into the following major examples:

• TaskBasedAsyncPattern
• TaskFoundations
• ErrorHandling
• AsyncStreams
• AsyncDesktopWindowsApp

All the sample projects have nullable reference types enabled.

WHY ASYNCHRONOUS PROGRAMMING IS IMPORTANT

Users find it annoying when an application does not immediately react to requests. As we scroll through a list, we have become accustomed to experiencing a delay because we've learned that behavior over several decades. We are accustomed to this behavior when using the mouse. However, with a touch UI, we often don't accept such a delay. An application with a touch UI needs to react immediately to requests. Otherwise, the user tries to redo the action, possibly by touching the screen more firmly.

Because asynchronous programming was hard to achieve with older versions of .NET, ...