Environments

• ASP.NET Core reads the environment variable ASPNETCORE_ENVIRONMENT at application startup and stores that value in IHostingEnvironment.EnvironmentName.
• ASPNETCORE_ENVIRONMENT can be set to any value, but three values are supported by the framework: Development, Staging, and Production.
• If ASPNETCORE_ENVIRONMENT isn't set, it will default to Production.

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        // Handle development settings.
    }

    if (env.IsProduction() || env.IsStaging() || env.IsEnvironment("Staging_2"))
    {
        // Handle other environments settings.
    }
}

• On Windows and macOS, environment variables and values are not case sensitive.
  • Linux environment variables and values are case sensitive by default.
• The environment for local machine development can be set in the *Properties\\launchSettings.json* file of the project.
  • Environment values set in launchSettings.json override values set in the system environment.
• The following JSON shows three profiles from a launchSettings.json file:

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "<http://localhost:54339/>",
      "sslPort": 0
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "WebApp1": {
      "commandName": "Project",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Staging"
      },
      "applicationUrl": "<http://localhost:54340/>"
    },
    "Kestrel Staging": {
      "commandName": "Project",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_My_Environment": "1",
        "ASPNETCORE_DETAILEDERRORS": "1",
        "ASPNETCORE_ENVIRONMENT": "Staging"
      },
      "applicationUrl": "<http://localhost:51997/>"
    }
  }
}

• When the application is launched with dotnet run, the first profile with "commandName": "Project" will be used.
  • The value of commandName specifies the web server to launch. commandName can be one of : IIS Express, IIS, and Project (which launches Kestrel).
• When an app is launched with dotnet run:
  • launchSettings.json is read if available environmentVariables settings in launchSettings.json override environment variables.
  • The hosting environment is displayed.

Setting the Environment

• If the environment isn't set, it will default to Production which disables most debugging features.
• The method for setting the environment depends on the operating system.

Azure App Services

• Select the Application settings blade.
• Add the key and value in App settings.

Windows

• To set the ASPNETCORE_ENVIRONMENT for the current session, if the app is started using dotnet run, the following commands are used

Command line:
set ASPNETCORE_E NVIRONMENT=Development

PowerShell:
$Env:ASPNETCORE_ENVIRONMENT = "Development"