You can have it as short as you want. For example check this minimal API https://learn.microsoft.com/en-us/aspnet/core/tutorials/min-web-api?view=aspnetcore-10

You can have it as short as you want. For example check this minimal API https://learn.microsoft.com/en-us/aspnet/core/tutorials/min-web-api?view=aspnetcore-10.0&tabs=visual-studio#add-the-api-code https://learn.microsoft.com/en-us/aspnet/core/tutorials/min-... — But if you want it to be mockable, concerns-separated and what have you, you’ll end up with at least 3-5 files. But it ain’t got nothing to do with either C# or .NET in general.