Application is running inside IIS process but is not configured to use IIS server .NET Core 3.0

Question

I have migrated our application from .NET Core 2.2 to version 3.0. Actually I created the new application in 3.0 from scratch and then copied source code files. Everything looks great but when I try to run the application within Visual Studio 2019 I get the exception:

Application is running inside IIS process but is not configured to use IIS server

Here is my Program.cs

public static class Program {     public static void Main(string[] args)     {         CreateHostBuilder(args).Build().Run();     }      public static IHostBuilder CreateHostBuilder(string[] args) =>         Host.CreateDefaultBuilder(args)             .ConfigureWebHostDefaults(webBuilder =>             {                 webBuilder.UseContentRoot(Directory.GetCurrentDirectory());                 webBuilder.UseKestrel();                 webBuilder.UseIISIntegration();                 webBuilder.UseStartup<Startup>();             }); } 

The error occurs at the line: CreateHostBuilder(args).Build().Run(); It worked fine in .NET Core 2.2 but it doesn't want to run as 3.0. I cannot find anything else that should be done. Something new in the Startup.cs? I don't know.

Answer 1

I also came across this issue while following the documentation https://docs.microsoft.com/en-us/aspnet/core/migration/22-to-30?view=aspnetcore-3.0&tabs=visual-studio

For your case I have checked and the code below will work, with the call to webBuilder.UseKestrel() removed.

public static IHostBuilder CreateHostBuilder(string[] args) =>        Host.CreateDefaultBuilder(args)            .ConfigureWebHostDefaults(webBuilder =>            {                webBuilder.UseContentRoot(Directory.GetCurrentDirectory());                webBuilder.UseIISIntegration();                webBuilder.UseStartup<Startup>();            });