Serilog in Azure Functions

Question

Each method in Azure Functions can have a Microsoft.Extensions.Logging.ILogger injected into it for logging. Using WebJobsStartup with a startup class you can change the logging to use Serilog using the following syntax:

[assembly: WebJobsStartup(typeof(Startup))]
namespace MyFuncApp {
    public class Startup : IWebJobsStartup
    {
        public void Configure(IWebJobsBuilder builder)
        {
            builder.Services.AddLogging(
                lb => lb.ClearProviders()
                    .AddSerilog(
                        new LoggerConfiguration()
                            .Enrich.FromLogContext()
                            .WriteTo.Console()
                            .WriteTo.File(@"C:\Temp\MyFuncApp.log")
                            .CreateLogger(),
                        true));
        }
    }
}

I can also add other objects to the DI and inject them either into the methods or into the constructor for the class containing the methods using i.e. builder.Services.AddSingleton<IMyInterface, MyImplementation>();

However, I would very much like to be able to inject the Microsoft.Extensions.Logging.ILogger in the same way, but if I try to use the ILogger in the constructor I get the following error during method invokation (as that's when the class is created):

Microsoft.Extensions.DependencyInjection.Abstractions: Unable to resolve service for type 'Microsoft.Extensions.Logging.ILogger' while attempting to activate 'MyFuncApp.MyFunctions'.

So, is there any way of injecting the ILogger into a class constructor like this?

public class MyFunctions
{
    private IMyInterface _myImpl;
    private ILogger _log;

    public MyFunctions(
        IMyInterface myImplememtation, // This works
        ILogger log) // This does not
    {
        _myImpl = myImplementation;
        _log = log;
        _log.LogInformation("Class constructed");
    }

    public async Task<IActionResult> Function1([HttpTrigger() ... ) {
        _log.LogInformation("Function1 invoked");
    }
}

Answer 1

It is possible to further simplify the necessary setup by using the package Anotar.Serilog.Fody (and any other Anotar package for that matter)

You need to set up Serilog all the same in the Startup class.

However, with the Fody package you can completely get rid of the injected logger

using Anotar.Serilog;

public class Functions
{
    [FunctionName("Token")]
    public async Task<IActionResult> Function1(
        [HttpTrigger()]...)
    {
        // static calls to the LogTo class
        // get translated into proper Serilog code during build
        LogTo.Information("Function1 invoked");
    }
}

Answer 2

Please try the code below, it works at my side:

    [assembly: WebJobsStartup(typeof(Startup))]
    namespace MyApp
 {
        public class Startup : IWebJobsStartup
        {
            public void Configure(IWebJobsBuilder builder)
            {
                //other code

                builder.Services.AddLogging();
            }
        }



    public class Functions
    {
        //other code
        private ILogger _log;

        public Functions(ILoggerFactory loggerFactory)
        {
            _log = loggerFactory.CreateLogger<Functions>();
        }

        [FunctionName("Token")]
        public async Task<IActionResult> Function1(
            [HttpTrigger()]...)
        {
               _log.LogInformation("Function1 invoked");
        }
    }

}

Answer 3

With AzureFunctions v3, the pattern you outlined in your question works out-of-the box.