Environment variable set but HostingEnvironment.EnvironmentName not updated

Question

Am running .net core 2.2 and hosting asp.net core within a windows service.
eg. see this https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/windows-service?view=aspnetcore-2.2&tabs=visual-studio

I set the environment variable ASPNETCORE_ENVIRONMENT to "Dev"

Just to confirm, within my launchsettings.json

  "environmentVariables": {
    "ASPNETCORE_ENVIRONMENT ": "Dev"
  }

When starting up the value of HostingEnvironment.EnvironmentName is not updated and still has "Production" which is default. Why is it not "Dev"?

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)                
        .ConfigureLogging((hostingContext, logging) =>
        {
            logging.AddEventLog();
        })
        .ConfigureAppConfiguration((context, config) =>
        {

            // Configure the app here.
            var env = context.HostingEnvironment;
            config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                              .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);

        })
        .UseStartup<Startup>();

}

You mean like a system level environment var? See above screenshot, I have the environment var set only in the IDE. — bitshift
Check Use multiple environments in ASP.NET Core. The docs explain that .NET Core recognized just three values for that environment variable, Development, Staging and Production. It could be that EnvironmentName is only set when the contents of the environment variable are recognized — Panagiotis Kanavos
The docs also explain that this setting is used to control several debugging features. The runtime has no idea what Dev means so the correct behavior would be to default to production - or throw. — Panagiotis Kanavos
We have environments like QA and UAT and those are set correctly. — juunas
Hopefully it's just a typo, but you've got a trailing space in ASPNETCORE_ENVIRONMENT in your launchSettings.json. — Kirk Larkin

ozzy ozzy · Accepted Answer · 2020-07-15T08:30:25

I spent quite a while trying to work out the best thing for me to do in this situation.

I ended up taking the code from Microsoft.Extensions.Hosting.Host.CreateDefaultBuilder and adding the .UseEnvironment extension on the builder.

            builder.UseEnvironment(Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Development");

I default to Development rather than the generally preferred Production, but that was personal preference.

It is limited and if you want to be clever and check for commandline arguments etc and so forth, feel free. It's a place to start.

public static IHostBuilder CreateDefaultBuilder(string[] args)
{
    var builder = new HostBuilder();

    // This line has been added to read the environment variable.
    builder.UseEnvironment(Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Development");

    builder.UseContentRoot(Directory.GetCurrentDirectory());
    builder.ConfigureHostConfiguration(config =>
    {
        config.AddEnvironmentVariables(prefix: "DOTNET_");
        if (args != null)
        {
            config.AddCommandLine(args);
        }
    });

    builder.ConfigureAppConfiguration((hostingContext, config) =>
    {
        var env = hostingContext.HostingEnvironment;

        config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);

        if (env.IsDevelopment() && !string.IsNullOrEmpty(env.ApplicationName))
        {
            var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName));
            if (appAssembly != null)
            {
                config.AddUserSecrets(appAssembly, optional: true);
            }
        }

        config.AddEnvironmentVariables();

        if (args != null)
        {
            config.AddCommandLine(args);
        }
    })
    .ConfigureLogging((hostingContext, logging) =>
    {
        var isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);

        // IMPORTANT: This needs to be added *before* configuration is loaded, this lets
        // the defaults be overridden by the configuration.
        if (isWindows)
        {
            // Default the EventLogLoggerProvider to warning or above
            logging.AddFilter<EventLogLoggerProvider>(level => level >= Microsoft.Extensions.Logging.LogLevel.Warning);
        }

        logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
        logging.AddConsole();
        logging.AddDebug();
        logging.AddEventSourceLogger();

        if (isWindows)
        {
            // Add the EventLogLoggerProvider on windows machines
            logging.AddEventLog();
        }
    })
    .UseDefaultServiceProvider((context, options) =>
    {
        var isDevelopment = context.HostingEnvironment.IsDevelopment();
        options.ValidateScopes = isDevelopment;
        options.ValidateOnBuild = isDevelopment;
    });

    return builder;
}

Environment variable set but HostingEnvironment.EnvironmentName not updated

1 Answers