Pass command-line arguments to Startup class in ASP.NET Core

You should be able to use the AddCommandLine() extension. First install the Nuget package Microsoft.Extensions.Configuration.CommandLine and ensure you have the correct import:

using Microsoft.Extensions.Configuration;

Now update your Main method to include the new config:

var config = new ConfigurationBuilder()
    .AddJsonFile("hosting.json", optional: true) //this is not needed, but could be useful
    .AddCommandLine(args)
    .Build();

var builder = new WebHostBuilder()
    .UseConfiguration(config)  //<-- Add this
    .UseStartup<Startup>()
    .UseKestrel()
    .UseUrls(listeningUrl);

Now you treat the command line options as configuration:

dotnet run /MySetting:SomeValue=123

And read in code:

var someValue = Configuration.GetValue<int>("MySetting:SomeValue");