UseStartup<Startup>() tells the ASP.NET Core host which Startup class configures dependency injection, middleware, and endpoints. section 30.7
Place it inside ConfigureWebHostDefaults when building an IHostBuilder. Startup separates frequently stable host bootstrapping from application configuration that changes as features grow. section 30.2
Register Startup in Program.cs
public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); }); section 30.2
The referenced Startup class typically provides:
- ConfigureServices(IServiceCollection) to register dependency-injection services. section 30.7
- Configure(IApplicationBuilder) to add middleware in pipeline order and register endpoints. section 30.7
