Program.cs Program.cs file is the entry point of application via Main() method. it also register Startup.cs class It also register IISIntegration and create a host using an instance of IWebHostBuilder Startup File Configure Service method: it configures services which are required by the app by using Configuration AppServices.it gets called by host before the "Configure" method the configuration app services Configure Method: It defines the apps request handling pipeline as a series of middleware components by using configure method. Depency Injection AddSingleton : Create only one instance when the service is requested for first time. And then the same. instance will be shared by all different http request. AddScoped : Create single instance for each request. For a different http request there will be a different instance. AddTransient : This instance is not shared at all.Every time a new instance will be created. What is Middleware? What is mean KES...