Which pattern to use for logging? Dependency Injection or Service Locator?

Question

Consider this scenario. I have some business logic that now and then will be required to write to a log.

interface ILogger
{
    void Log(string stuff);
}

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Answer 1

The logger is clearly a service that your business logic depends upon, and should thus be treated as a dependency the same way you do with IDependency. Inject the logger in your constructor.

Note: even though AOP is mentioned as the way to inject logging I do not agree that it is the solution in this case. AOP works great for execution tracing, but will never be a solution for logging as part of business logic.