Are you a web developer or do you write Internet of things (IoT) software? If so, you would know that many web and IoT development projects these days require the ability to establish a persistent connection between a client and a server without having to keep sending repeated requests from the client. For example, a user of a live chat would want to know in real time that they have received a new message. Or an IoT device may need to be sent a command in real time.

As you may also know, such functionality may be hard to implement. However, if you can build your server-side application on ASP.NET Core, there is a way to make this whole process easy. There is a library called SignalR, which is included in ASP.NET Core.

SignalR doesn't only enable you to achieve real-time two-way communication between applications. It also substantially simplifies the process of enabling all of this in the code. Under the hood, it uses various two-way communication protocols, such as WebSocket. However, it abstracts away all the implementation complexity of these protocols. To the developer, working with this library will mostly consists of writing simple and easily readable statements.

In this book, we will cover everything you would need to know about using SignalR on .NET 6, so you will see how to integrate it with the the latest features on ASP.NET Core 6 and C# 10. We will cover much more than you can find in the official documentation of the library. For example, you will learn how to connect a plain WebSocket client to it, which may help you to write a client in a language that isn't officially supported. Likewise, we will cover many concepts that aren't directly related to SignalR, but are important to its production-ready implementation. These would include single sign-on, certificate authorization, logging, metrics and scaling out. By the end of this book, you would be able to identify the situations where SignalR is the best tool for the job and you would be fully able to implement it.

Design patters are something that you will need to get familiar with as a programmer who works with object oriented languages. And this is primarily because they represent well-defined solutions to common software development problems. So, instead of thinking through all the details of your solution, you can simply check if any of the existing design patterns can be used. You won’t have to reinvent the wheel.

The main problem with design patterns is that they are not necessarily easy to learn. Many developers, especially the ones who don’t have a lot of software-building experience, struggle with them. But if you do struggle with them, it may prevent you from getting a programming job at a reputable organization. After all, recruiting managers often ask questions about design patterns. Otherwise, not knowing design patterns will make you less effective as a software developer, which will slow down your career progress.

The main reason why design patterns are so hard to learn is because of the way they are normally taught. Usually, if you pick pretty much any book on design patterns or open pretty much any online article about them, it would provide a collection of design patterns that you would need to go through. You would then have to got through each of them, try your best to understand the principles behind it and only then try to figure out how to apply it in a real-life situation.

It's a tedious process that doesn't always bring about the right results. It's not uncommon for software developers to memorize just a handful of design patterns that they have been using in their own projects. The remaining ones have been forgotten as soon as they've been learned. And it's hard to figure out which design pattern applies in which situation if you only remember a handful of them.

This book provides a different approach. It uses a methodology that makes it easy to learn design patterns. So, you no longer have to brute-force your way through them. The process of effective learning is not about memorization. It's about associations. You learn new things easily when you can clearly see how new facts related to your existing knowledge. And this is precisely the method that this book is built around.

You won't have to brute-force your way into design patterns. In fact, you won't even start with the design patterns. First, we will go through a list of common problems that software developers are required to solve. Those are the things that every software developer can associate with. Even if you haven't faced a particular type of a problem yet, you will still be able to easily understand its description. For each of these problems, we will go through the design patterns that can solve it. And for each one of them, you will go through its core principle and the description of how it can solve this type of a problem. Only then you will be invited to examine this particular design pattern in detail, so you can understand how to implement it in your own code.

This structure of the book also makes it valuable as a reference book. Even when you don't know or don't remember design patterns, looking them up becomes easy. What you need to find is a description of the type of a problem you are trying to solve. And then you will be able to follow it to find the actual design patterns that you can apply to solve it.

Therefore this book is not only an effective learning tool. It's also a reference book that's incredibly easy to navigate. It's been structured in such a way that you'll be able to find the right answer in seconds.