The name of the Startup class is a convention of ASP.NET Core applications. It is recommended to leave it as it is to make the code clearer for colleagues. However, there are a few situations where you are required to use a different name for the Startup class—for example, when Startup is already a class in your application but is responsible for an entirely different task than initializing ASP.NET Core.

On such occasions, open the Program class file, located in the root folder under Program.cs, and locate the CreateWebHostBuilder method. It should look similar to the following:

 public static IWebHostBuilder CreateWebHostBuiler(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .UseStartup<Startup>();

In order to point ASP.NET Core to a different class name, for example, to CustomStartup, change the UseStartup<Startup>() line to UseStartup<CustomStartup>:

public static IWebHostBuilder CreateWebHostBuiler(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .UseStartup<Startup>();