Read environment variables in ASP.NET Core

Question

Running my ASP.NET Core application using DNX, I was able to set environment variables from the command line and then run it like this:

set ASPNET_ENV = Prod         


        

Answer 1

This should really be a comment to this answer by @Dmitry (but it is too long, hence I post it as a separate answer):

You wouldn't want to use 'ASPNETCORE_ENVIRONMENT ' (with a trailing space) - there are features in ASP.NET Core which depend on the value of 'ASPNETCORE_ENVIRONMENT'(no trailing space) - e.g. resolving of appsettings.Development.json vs appsettings.Production.json. (e.g. see Working with multiple environments documentation article

And also I guess if you'd like to stay purely inside ASP.NET Core paradigm, you'd want to use IHostingEnvironment.Environment(see documentation) property instead of reading from Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") directly (although the former is of course set from the latter). E.g. in Startup.cs

public class Startup
{
    //<...>

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        Console.WriteLine("HostingEnvironmentName: '{0}'", env.EnvironmentName);
        //<...>
    }

    //<...>
}