Understanding the generic host

Starting with version 3.0, ASP.NET Core is now bootstrapped using a generic host. This means that it is not tied specifically to HTTP or any other web protocol, but it potentially supports any kind of protocol, including low-level TCP. The templates have changed and now the bootstrap looks something like this:

Host
 .CreateDefaultBuilder(args)
 .ConfigureWebHostDefaults(webBuilder =>
 {
     webBuilder.UseStartup<Startup>();
 });

We are now using the Host class to create an instance of a class that implements IHostBuilder, not IWebHostBuilder, although the result is the same.

We can interfere in the bootstrap process by means of extension methods. Specifically, we can configure the following:

• Services registration
• Logging
• Configuration
• Web hosting defaults (host, startup class)

Here is a full example of changing the configuration:

Host
    .CreateDefaultBuilder...