ASPNETCOREENVIRONMENT

ASPNETCORE_ENVIRONMENT is an environment variable used by ASP.NET Core applications to indicate the hosting environment in which the app is running. The value influences how the application loads configuration, which services are enabled, and how middleware behaves, particularly during startup and error handling. It enables environment-specific behavior and settings without changing code.

Common environment names are Development, Staging, and Production. Development typically enables detailed error pages and debugging aids, while Production uses generic error handling and stricter security. If the variable is not set, ASP.NET Core defaults to Production, providing a safer baseline for deployments.

In code, the current environment is exposed through IHostEnvironment (or IWebHostEnvironment) via the EnvironmentName property. There are convenience methods such as IsDevelopment(), IsStaging(), and IsProduction() to perform conditional logic. This allows developers to enable or disable features like the Developer Exception Page or detailed logging depending on the environment.

Setting the variable is straightforward. On Windows, in a command prompt, you can set ASPNETCORE_ENVIRONMENT=Development before launching the app; to persist this setting, tools like setx can be used. On Linux or macOS, you would export ASPNETCORE_ENVIRONMENT=Development in the shell before running the app. In IIS hosting scenarios, the value can also be supplied via web.config as an environmentVariable.

Best practices include pairing the environment with environment-specific configuration files such as appsettings.Development.json and appsettings.Production.json, and keeping sensitive information out of non-production environments. This approach helps ensure correct behavior and safer operation across development, staging, and production.