These two methods will declare in Global.asax file as shown belowpublic class WebApiApplication : System.Web.HttpApplication{protected void Application_Start(){//Any Initializations of resources before calling any functionality}protected void Application_End(){//Release of resources before unloading the application}}Application_Start() method is called when the first resource of the application is requested and it is called once for the application. There is no “user perspective” in this. Just load/create stuff needed for the application to function.Similarly, Application_End() method is called only once, before the application is unloaded. Use it to dispose of resources.

It is by default feature in Global.ascx file.