.NET Core has the notion of environment. An environment is basically a runtime setting in the form of an environment variable called ASPNETCORE_ENVIRONMENT. This variable can take one of the following values (case-sensitive):

To be correct, you can pass any value, but these have particular significance to .NET Core. There are several ways by which you can access the current environment, but you're most likely to use one of the following methods, extensions methods and properties of the IHostingEnvironment interface:

The IsDevelopment, IsProduction, and IsStaging extension methods are just convenience methods using the IsEnvironment method. Based on the actual environment you can make decisions on the code, such as pick a different connection string, web service URL, and so on. It is important to point out that this has nothing to do with Debug or Release compiler configurations.

You normally get an instance of IHostingEnvironment from the Configure method:

    public void Configure(IApplicationBuilder app,
     IHostingEnvironment env) { /* ... */ }

But also from the constructor of the Startup class:

    public Startup(IHostingEnvironment env) { /* ... */ }

Or even from the dependency injection framework, which is available from the HttpContext class, among other places:

    var env = 
      HttpContext.RequestServices.GetService<IHostingEnvironment>();

A final note, service configuration plays well with environments. Instead of a single ConfigureServices method, we can have multiple methods, named ConfigureDevelopmentServices, ConfigureStagingServices, and ConfigureProductionServices. A nice feature that can help us better organize our code!