AppConfig

Appconfig is a general term for the data an application uses to determine its behavior without changing code. This configuration can be stored in files, provided by environment variables, or supplied through command-line arguments, and it is typically read at startup or when a configuration refresh is triggered. Common formats include XML, JSON, YAML, and INI, with environment variables and secret stores often integrated for security and flexibility.

In the .NET ecosystem, app.config traditionally refers to the XML-based configuration file used by .NET Framework applications. When a project is built, app.config is copied and renamed to the executable’s .exe.config in the output directory, where it can define settings, connection strings, and custom configuration sections. For web applications, web.config serves a similar role. Since the introduction of .NET Core, developers have moved toward a more flexible configuration model based on appsettings.json and environment-specific overrides, accessed via a configuration API rather than relying on the older app.config approach.

Across ecosystems, configuration systems typically support hierarchical keys, sections, and multiple providers. This enables layered configurations, where defaults can be overridden by environment variables, user secrets, or remote configuration systems. Modern frameworks also offer strongly-typed options or binding facilities to map configuration data to typed objects, improving validation and maintainability.

Security and governance considerations are central to appconfig practices. Secrets should generally not be stored in plain text in configuration files; instead, credentials should be retrieved from secure stores or injected at runtime. Validation, versioning, and environment-specific configurations are common strategies to reduce risk and ensure predictable behavior across deployments.