Step by step migration of ASP.NET Core 2.2 to 3.1
In order to upgrade/migrate asp.net core version to 3.1 following steps to be perform. Download and install Visual Studio 2019 version 16.4 or higher. Download and install .NET Core 3.1 https://dotnet.microsoft.com/download/dotnet-core/3.1 Upgrade the projects of solution to .NET Core 3.1 , because ASP.NET Core 3.1 requires it. Update existing Nuget packages to a version compatible with ASP.NET Core 3.1 in each project Use IHost interface from a IHostBuilder instead of building and running a IWebHost from a IWebHostBuilder in Program.cs public static IHostBuilder CreateWebHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseKestrel() .UseSerilog() .UseStartup<Startup>(); }) Change AddMvc method has been replaced by AddControllers in Startup.cs of each projects. In Startup.cs, UseMvc method to b