Application development has evolved over the last decade, and with the advent of the latest technologies like Angular, React on client-side, and ASP.NET Core, Spring on the server-side, the consumer expectations have risen like never before. The primary objective of this book is to help readers understand the importance of asynchronous programming and various ways it can be achieved using .NET Core 3.1 and C# 8 to successfully build concurrent applications. Along the way reader will learn the fundamentals of threading, asynchronous programming, various asynchronous patterns, synchronisation constructs, unit testing parallel methods, debugging enterprise applications, and cool tips and tricks.There are samples based on practical examples that will help the reader effectively use parallel programming. By the end of this book, you will be equipped with all the knowledge needed to understand, code, and debug multithreaded, concurrent and parallel programs with confidence.