How to set Environment Name (IHostingEnvironment.EnvironmentName)?

Question

Default ASP.NET Core web project contain such lines in Startup.cs:

if (string.Equals(env.EnvironmentName, "Development", StringComparison.OrdinalIgnoreCase)) {     app.UseBrowserLink();     app.UseDeveloperExceptionPage(ErrorPageOptions.ShowAll); } else {     app.UseExceptionHandler("/Home/Error"); } 

As I understand, the EnvironmentName is a new way to handle Dev/Production environment. But it doesn't changes on Release build configuration. So what is the way to set a different EnvironmentName?

I can imagine that it should be set in "Commands" as a parameter for server.

Answer 1

After RC2

So what is the way to set a different EnvironmentName?

Set the ASPNETCORE_ENVIRONMENT environmental variable.

There are many ways to set that environmental variable. These include a launchSettings.json profile and other environment-specific ways. Here are some examples.

From a console:

// PowerShell > $env:ASPNETCORE_ENVIRONMENT="Development"  // Windows Command Line > SET ASPNETCORE_ENVIRONMENT=Development  // Bash > ASPNETCORE_ENVIRONMENT=Development 

From an Azure Web App's App settings:

Before RC2

I can imagine that it should be set in "Commands" as a parameter for server.

That is true. In your project.json, add --ASPNET_ENV production as a parameter for the server.

"commands": {   "web": "Microsoft.AspNet.Hosting --ASPNET_ENV production --server Microsoft.AspNet.Server.WebListener --server.urls http://localhost:5001" } 

Now when you run dnx . web from the command line, ASPNET_ENV will be production.

Relevant ASP.NET Core Hosting Source Code

The WebHostBuilder combines "ASPNETCORE_" with the WebHostDefaults.EnvironmentKey to make "ASPNETCORE_environment". It also supports the legacy keys.

WebHostDefaults.cs

namespace Microsoft.AspNetCore.Hosting {     public static class WebHostDefaults     {         public static readonly string ApplicationKey = "applicationName";         public static readonly string StartupAssemblyKey = "startupAssembly";          public static readonly string DetailedErrorsKey = "detailedErrors";         public static readonly string EnvironmentKey = "environment";         public static readonly string WebRootKey = "webroot";         public static readonly string CaptureStartupErrorsKey = "captureStartupErrors";         public static readonly string ServerUrlsKey = "urls";         public static readonly string ContentRootKey = "contentRoot";     } } 

WebHostBuilder.cs

_config = new ConfigurationBuilder()     .AddEnvironmentVariables(prefix: "ASPNETCORE_")     .Build();  if (string.IsNullOrEmpty(GetSetting(WebHostDefaults.EnvironmentKey))) {     // Try adding legacy environment keys, never remove these.     UseSetting(WebHostDefaults.EnvironmentKey,          Environment.GetEnvironmentVariable("Hosting:Environment")          ?? Environment.GetEnvironmentVariable("ASPNET_ENV")); } 

Backward Compatibility

The environment key is set with the ASPNETCORE_ENVIRONMENT environment variable. ASPNET_ENV and Hosting:Environment are still supported, but generate a deprecated message warning.

https://docs.asp.net/en/latest/migration/rc1-to-rtm.html

Default Value

The default value is "Production" and is set here.