Professional C# and .NET, 2021st Edition

28SignalR

WHAT'S IN THIS CHAPTER?

• Overview of SignalR
• Creating a SignalR hub
• Creating a SignalR client with HTML and JavaScript
• Creating a SignalR .NET client
• Using groups with SignalR
• Streaming with SignalR

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 3_Web/SignalR.

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

• SignalRSample/ChatServer
• SignalRSample/WinAppChatClient
• SignalRStreaming

The major namespace used is Microsoft.AspNetCore.SignalR. All the projects have nullable reference types enabled.

OVERVIEW

With .NET you can use events to get notifications. You can register an event handler method with an event, also known as subscribing to an event, and as soon as the event is fired from another place, your method gets invoked. Events cannot be used with web applications.

Previous chapters covered a lot about web applications and web services. What was common with these applications and services is that the request was always started from the client application. The client makes an HTTP request and receives a response.

What if the server has some news to tell? There's nothing like events that you can subscribe to, or is there? With the web technologies you've seen so far, this can be resolved by the client polling for new information. ...