Looking a project that uses Common.Logging for .NET, I noticed that some classes declare the logger instance as a class static member. For instance:

public class HelloJob : IJob
{
    private static ILog _log = LogManager.GetLogger(typeof(HelloJob));

    public HelloJob()
    {
    }

    public virtual void  Execute(IJobExecutionContext context)
    {
        _log.Info(string.Format("Hello World! - {0}", System.DateTime.Now.ToString("r")));
    }
}

And in other classes the logger is declared as an instance member:

public class SimpleExample : IExample
{
    public virtual void Run()
    {
        ILog log = LogManager.GetLogger(typeof (SimpleExample));

        log.Info("------- Initializing ----------------------");

        // etc
    }
}

Is there a reason to prefer one approach or the other?

In which cases is each approach recommended? Is it related to thread safety?

Would it be a problem if I just declared a "Logger" class with a static "logger" member and the whole project used that (apart from the issue that I would in practice have a global variable)?

c# logging common.logging
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