CODEWITHSUNDEEP
loggingasp.net-core
Set
Set

Reputation: 49779

Why ASP.NET Core DI knows how to resolve ILogger<T>, but not ILogger?

If class T contains dependency on ILogger, dependency is resolved:

public class Foo
{
    private ILogger _logger;

    public Foo(ILogger<Foo> logger)
    {
        _logger = logger;
    }
}

but the following does not work, as logger will be null:

public class Foo
{
    private ILogger _logger;

    public Foo(ILogger logger)
    {
        _logger = logger;
    }
}

Upvotes: 30

Views: 11072

Answers (2)

adem caglin
adem caglin

Reputation: 24073

Your first scenerio works because ILogger<> inherits from ILogger(see source code)

public interface ILogger<out TCategoryName> : ILogger
{

}

But as @KiranChalla said, in the LoggingServiceCollectionExtensions ILogger<> is registered(not ILogger) so your second scenerio does not work.

Upvotes: 2

Kiran
Kiran

Reputation: 57949

Logging adds the following services to DI

services.TryAdd(ServiceDescriptor.Singleton<ILoggerFactory, LoggerFactory>());
services.TryAdd(ServiceDescriptor.Singleton(typeof(ILogger<>), typeof(Logger<>)));

and Logger<> depends on ILoggerFactory from DI.

For your second scenario you would need to inject ILoggerFactory instead of ILogger.

public Foo(ILoggerFactory loggerFactory)
{
    _logger = loggerFactory.CreateLogger("logger name here");
}

Upvotes: 22

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