ASP.NET Core Web API Logging from a Static Class

问题

I'm logging just fine using dependency injection on my controllers, now I need to log something from a static class.

How can I log from a static class?

I can't use dependency injection because it's static and I can't just pass in an existing logger object to the static class because it would have the wrong name of class in the log file.

In other words how can I get a logger from the loggerfactory inside my static class?

I came across a similar question and they pointed to an article on a loggerfactory in a static class but that doesn't actually work as I can't get a new logger from it because it won't accept a static class as the parameter:

"Static types cannot be used as type arguments"

回答1:

Solution is to have a static reference to the LoggerFactory in a utility static class initialized on startup:

/// <summary>
    /// Shared logger
    /// </summary>
    internal static class ApplicationLogging
    {
        internal static ILoggerFactory LoggerFactory { get; set; }// = new LoggerFactory();
        internal static ILogger CreateLogger<T>() => LoggerFactory.CreateLogger<T>();        
        internal static ILogger CreateLogger(string categoryName) => LoggerFactory.CreateLogger(categoryName);

    }

Which you intialize on Startup.cs:

 public Startup(ILogger<Startup> logger, ILoggerFactory logFactory, IHostingEnvironment hostingEnvironment)
        {
            _log = logger;
            _hostingEnvironment = hostingEnvironment;
            Util.ApplicationLogging.LoggerFactory = logFactory;//<===HERE

        }

Then you can build a logger to use from your static class like so:

internal static class CoreJobSweeper
    {
        private static ILogger log = Util.ApplicationLogging.CreateLogger("CoreJobSweeper");

回答2:

You can use the static LoggerFactory instance with the following extension method which accepts a regular parameter of type Type, rather than a generic type parameter: CreateLogger(ILoggerFactory, Type)

i.e. loggerFactory.CreateLogger(typeof(T)) rather than loggerFactory.CreateLogger<T>()

回答3:

First of all, I agree with NightOwl888 answer.

But as an option (consider this as a workaround) you could inject ILogger dependency via method parameter => so a class that will call this static method should be responsible for providing a correct implementation of ILogger.

static class YourClass
{
    public static void DoSomething(ILogger logger)
    {
         // do something
         // call log.Log();
    }
}

来源：https://stackoverflow.com/questions/48676152/asp-net-core-web-api-logging-from-a-static-class