Write Asynchronous C# Code With Tasks and PLINQ

Welcome to the Multi-Threaded Code Fundamentals section. I will give a quick introduction on how the section is organized before we get started.

In this lecture I will teach you how to start new threads using the System.Thread class: the workhorse of multi-threaded programming in C#.

I will also show you how you can give a descriptive name to a thread, to aid in debugging.

Finally, you will learn that there are two classes of threads: foreground- and background threads. I will show you the difference in behaviour between these two classes of threads.

In this lecture I am going to show you the most common multi-threading programming problem: a race condition.

A race condition happens when 2 or more threads are trying to access and modify the same variable. I will demonstrate a race condition with a very simple program, with 2 threads accessing a shared integer class member.

In this lecture we are going to take a closer look at the lock statement in C#. You will learn that "lock" is in fact syntactic sugar for a pair of Monitor.Enter and Monitor.Exit calls. I will demonstrate several example programs using either the compact "lock" syntax, or the more verbose code that uses the Monitor class.

You will learn all the essentials of thread locking, including what code to lock, which synchronisation object to use, and what the advantages are of calling the Monitor class directly.

By the end of the lecture you will be proficient in thread locking, and you will be able to set up critical sections in your code with ease.

In this lecture I am going to take a look at thread synchronisation. The need for thread synchronisation arises when two or more threads need to exchange data in a controlled manner. I will show you a simple example program that attempts to exchange data between threads without any synchronisation, and you will see how the data transfer completely fails.

Next we will cover the workhorse of thread synchronisation: the AutoResetEvent. I will show you how you can line up two threads with a single AutoResetEvent variable, to ensure that you'll never lose any data. Then I'll show you how the single remaining race condition can be resolved by adding a second AutoResetEvent.

By the end of the lecture you will have a deep understanding of thread synchronisation: what it is, when you need it, and how you can implement it yourself.

Congratulations on finishing this section. This is a recap of what we have learned.

Welcome to the Working With Tasks section. I will give a quick introduction on how the section is organized before we get started.

In this lecture we're going to take a closer look at tasks. We have already encountered generic tasks that can return a value to another thread. This lecture will introduce non-generic tasks that run asynchronously in the background without returning any data. I'll show you how to start a non-generic task and wait for it to complete.

I'll also demonstrate how the .NET runtime uses a thread pool to execute tasks, and how you can fine-tune how threads are assigned to tasks. Finally we'll discover what happens when a task throws an exception.

In this lecture I will show you how to start a task with initialisation data. You will also learn how to cancel a running task by using a cancellation token.

The nice thing about the Task Parallel Library is that you can connect together thousands of tasks into complex patterns. In this lecture you will learn how you can create hierarchies of parent and child tasks.

I will show you how to write a simple program that reverses the characters in each word using parent and child tasks.

The Task Parallel Library lets you connect together thousands of tasks into complex patterns. In this lecture you will learn how you can create sequences of tasks with continuations. By combining task hierarchies with continuations you can implement any MapReduce problem in C#.

I will revisit the word reversing program from the previous lecture. I will use continuations and child tasks to rewrite the code as a MapReduce solution.

There are three asynchronous libraries that you can use in C#: the Task Parallel Library, the Parallel class, and the Parallel LINQ library. Sometimes it can be difficult to choose between them.

In this lecture we are going to take a closer look at the pros and cons of the Task Parallel Library. By the end of the lecture you will know exactly when to use this Library.

Congratulations on finishing this section. This is a recap of what we have learned.

There are three asynchronous libraries that you can use in C#: the Task Parallel Library, the Parallel class, and the Parallel LINQ library. Sometimes it can be difficult to choose between them.

In this lecture we are going to take a closer look at the pros and cons of the Parallel LINQ library. By the end of the lecture you will know when to use this library.

In the previous lecture I showed you how to reimplement the word reversal program in PLINQ. But there was something wrong with the final result, when I used WithExecutionMode to force PLINQ to run the query on multiple threads.

In this lecture we are going to revisit those results, analyse what went wrong and attempt to fix the program to produce the correct output.

By the end of the lecture you will understand exactly how PLINQ affects item ordering.

PLINQ is an extremely powerful library. It valiantly attempts to parallelise every LINQ query you throw at it but sometimes it simply cannot execute a query on multiple threads.

When a query is too complex PLINQ will silently fall back to sequential mode and execute the entire query on a single thread. When this happens PLINQ will actually be slightly slower than regular LINQ!

In this lecture we will identify all the scenarios in which PLINQ falls back to sequential mode. By the end of the lecture you will know which queries should not be parallelised.

Congratulations on finishing this section. This is a recap of what we have learned.

In this lecture I would like to thank you for finishing the course and offer some final words.

Check out The Machine Learning Advantage, my amazing new program that will help you become an expert C# AI developer!