Specifying Environment from the Command Line in ASP.NET Core

ASP.NET Core picks up the environment from the environment variable ASPNETCORE_ENVIRONMENT. If you want to set it from Visual Studio, you can do so by double clicking “Properties” in Solution Explorer > Debug > Environment Variables. Just add an entry with a name of “ASPNETCORE_ENVIRONMENT” and a value desired.

If you want to set the environment from the command line, you have to modify the Main method like this.

public static void Main(string[] args)
{
    var config = new ConfigurationBuilder().AddCommandLine(args).Build();

    var host = new WebHostBuilder()
        .UseConfiguration(config)
        .UseKestrel()
        .UseStartup<Startup>()
        .Build();

    host.Run();
}

With that, you can pass the environment, like so.

dotnet run --environment "UAT"

You can also specify server URL using command line.

dotnet run --environment UAT --server.urls http://*:5001

That will set the environment to “UAT” and let Kestrel use port 5001.