ILoggerFactory

ILoggerFactory is an interface in the Microsoft.Extensions.Logging namespace that represents a factory for creating ILogger instances and coordinating logging providers. Its primary role is to supply loggers and to manage the set of providers that actually perform the logging work. The interface typically exposes a method to create a logger for a given category name and a method to register logging providers. In common implementations, it includes CreateLogger(string categoryName) and AddProvider(ILoggerProvider provider). It also implements IDisposable to allow proper resource cleanup when the factory is no longer needed.

Providers and logging pipeline: The factory delegates logging to a collection of ILoggerProvider instances. Each provider implements the details of how and where log messages are written (for example, to the console, debug output, or a file) and respects configured log levels and filters. By aggregating providers, the factory enables a unified configuration for multiple destinations.

Typical usage: In modern .NET applications, logging configuration is usually wired up through a host or service container, which registers one or more providers and creates loggers automatically. Developers can obtain an ILoggerFactory via dependency injection, or create and use a logger directly through the factory by calling CreateLogger with a category name. For many scenarios, injecting ILogger<T> into a component is preferred, with the framework resolving the appropriate logger category.

Relationship to other components: ILoggerFactory works with ILogger and ILoggerProvider. The factory creates loggers that use one or more providers to emit log events, enabling flexible, extensible logging across applications.