Book Image

Multithreading with C# Cookbook, Second Edition - Second Edition

By : Evgenii Agafonov
Book Image

Multithreading with C# Cookbook, Second Edition - Second Edition

By: Evgenii Agafonov

Overview of this book

Multi-core processors are synonymous with computing speed and power in today’s world, which is why multithreading has become a key concern for C# developers. Multithreaded code helps you create effective, scalable, and responsive applications. This is an easy-to-follow guide that will show you difficult programming problems in context. You will learn how to solve them with practical, hands-on, recipes. With these recipes, you’ll be able to start creating your own scalable and reliable multithreaded applications. Starting from learning what a thread is, we guide you through the basics and then move on to more advanced concepts such as task parallel libraries, C# asynchronous functions, and much more. Rewritten to the latest C# specification, C# 6, and updated with new and modern recipes to help you make the most of the hardware you have available, this book will help you push the boundaries of what you thought possible in C#.
Table of Contents (18 chapters)
Multithreading with C# Cookbook Second Edition
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Handling exceptions


This recipe will describe how to handle exceptions in other threads properly. It is very important to always place a try/catch block inside the thread because it is not possible to catch an exception outside a thread's code.

Getting ready

To work through this recipe, you will need Visual Studio 2015. There are no other prerequisites. The source code for this recipe can be found at BookSamples\Chapter1\Recipe11.

How to do it...

To understand the handling of exceptions in other threads, perform the following steps:

  1. Start Visual Studio 2015. Create a new C# console application project.

  2. In the Program.cs file, add the following using directives:

    using System;
    using System.Threading;
    using static System.Console;
    using static System.Threading.Thread;
  3. Add the following code snippet below the Main method:

    static void BadFaultyThread()
    {
      WriteLine("Starting a faulty thread...");
      Sleep(TimeSpan.FromSeconds(2));
      throw new Exception("Boom!");
    }
    
    static void FaultyThread()
    {
      try
      {
        WriteLine("Starting a faulty thread...");
        Sleep(TimeSpan.FromSeconds(1));
        throw new Exception("Boom!");
      }
      catch (Exception ex)
      {
        WriteLine($"Exception handled: {ex.Message}");
      }
    }
  4. Add the following code snippet inside the Main method:

    var t = new Thread(FaultyThread);
    t.Start();
    t.Join();
    
    try
    {
      t = new Thread(BadFaultyThread);
      t.Start();
    }
    catch (Exception ex)
    {
      WriteLine("We won't get here!");
    }
  5. Run the program.

How it works...

When the main program starts, it defines two threads that will throw an exception. One of these threads handles an exception, while the other does not. You can see that the second exception is not caught by a try/catch block around the code that starts the thread. So, if you work with threads directly, the general rule is to not throw an exception from a thread, but to use a try/catch block inside a thread code instead.

In the older versions of .NET Framework (1.0 and 1.1), this behavior was different and uncaught exceptions did not force an application shutdown. It is possible to use this policy by adding an application configuration file (such as app.config) that contains the following code snippet:

<configuration>
  <runtime>
    <legacyUnhandledExceptionPolicy enabled="1" />
  </runtime>
</configuration>