You execute `AddMvc`. This is not recommended in dotnetcore 3.0, since it is done via `AddControllersWithViews`    Remove the `AddMvc` call and replace the `AddControllersWithViews` with:    ```csharp              services.AddControllersWithViews()                  .AddApplicationPart(assembly)                  .AddRazorRuntimeCompilation();  ```    I tested it and also works.