How to get the Development/Staging/production Hosting Environment in ConfigureServices

You can easily access it in ConfigureServices, just persist it to a property during Startup method which is called first and gets it passed in, then you can access the property from ConfigureServices.

public Startup(IHostingEnvironment env, IApplicationEnvironment appEnv)
{
    ...your code here...
    CurrentEnvironment = env;
}

private IHostingEnvironment CurrentEnvironment{ get; set; } 

public void ConfigureServices(IServiceCollection services)
{
    string envName = CurrentEnvironment.EnvironmentName;
    ... your code here...
}

TL;DR

Set an environment variable called ASPNETCORE_ENVIRONMENT with the name of the environment (e.g. Production). Then do one of two things:

• Inject IHostingEnvironment into Startup.cs, then use that (env here) to check: env.IsEnvironment("Production"). Do not check using env.EnvironmentName == "Production"!
• Use either separate Startup classes or individual Configure/ConfigureServices functions. If a class or the functions match these formats, they will be used instead of the standard options on that environment.
  • Startup{EnvironmentName}() (entire class) || example: StartupProduction()
  • Configure{EnvironmentName}() || example: ConfigureProduction()
  • Configure{EnvironmentName}Services() || example: ConfigureProductionServices()

---

Full explanation

The .NET Core docs describe how to accomplish this. Use an environment variable called ASPNETCORE_ENVIRONMENT that's set to the environment you want, then you have two choices.

Check environment name

From the docs:

The IHostingEnvironment service provides the core abstraction for working with environments. This service is provided by the ASP.NET hosting layer, and can be injected into your startup logic via Dependency Injection. The ASP.NET Core web site template in Visual Studio uses this approach to load environment-specific configuration files (if present) and to customize the app’s error handling settings. In both cases, this behavior is achieved by referring to the currently specified environment by calling EnvironmentName or IsEnvironment on the instance of IHostingEnvironment passed into the appropriate method.

NOTE: Checking the actual value of env.EnvironmentName is not recommended!

If you need to check whether the application is running in a particular environment, use env.IsEnvironment("environmentname") since it will correctly ignore case (instead of checking if env.EnvironmentName == "Development" for example).

Use separate classes

From the docs:

When an ASP.NET Core application starts, the Startup class is used to bootstrap the application, load its configuration settings, etc. (learn more about ASP.NET startup). However, if a class exists named Startup{EnvironmentName} (for example StartupDevelopment), and the ASPNETCORE_ENVIRONMENT environment variable matches that name, then that Startup class is used instead. Thus, you could configure Startup for development, but have a separate StartupProduction that would be used when the app is run in production. Or vice versa.

In addition to using an entirely separate Startup class based on the current environment, you can also make adjustments to how the application is configured within a Startup class. The Configure() and ConfigureServices() methods support environment-specific versions similar to the Startup class itself, of the form Configure{EnvironmentName}() and Configure{EnvironmentName}Services(). If you define a method ConfigureDevelopment() it will be called instead of Configure() when the environment is set to development. Likewise, ConfigureDevelopmentServices() would be called instead of ConfigureServices() in the same environment.

In .NET Core 2.0 MVC app / Microsoft.AspNetCore.All v2.0.0, you can have environmental specific startup class as described by @vaindil but I don't like that approach.

You can also inject IHostingEnvironment into StartUp constructor. You don't need to store the environment variable in Program class.

public class Startup
{
    private readonly IHostingEnvironment _currentEnvironment;
    public IConfiguration Configuration { get; private set; }

    public Startup(IConfiguration configuration, IHostingEnvironment env)
    {
        _currentEnvironment = env;
        Configuration = configuration;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        ......

        services.AddMvc(config =>
        {
            // Requiring authenticated users on the site globally
            var policy = new AuthorizationPolicyBuilder()
                .RequireAuthenticatedUser()
                .Build();
            config.Filters.Add(new AuthorizeFilter(policy));

            // Validate anti-forgery token globally
            config.Filters.Add(new AutoValidateAntiforgeryTokenAttribute());

            // If it's Production, enable HTTPS
            if (_currentEnvironment.IsProduction())      // <------
            {
                config.Filters.Add(new RequireHttpsAttribute());
            }            
        });

        ......
    }
}