Is it possible to get an ILogger inside Program.cs Main method? I want to pass it on to a service that's created inside that method.
I've only found this on SO How do I write logs from within Startup.cs , but that's logging within Startup.cs.
-
1See the official docs learn.microsoft.com/en-us/aspnet/core/fundamentals/logging/…RickAndMSFT– RickAndMSFT2022-06-15 23:06:21 +00:00Commented Jun 15, 2022 at 23:06
Add a comment
|
7 Answers
Accidentally stumbled upon the answer after googling a bit more.
using System;
using Microsoft.Extensions.Logging;
namespace ConsoleApplication
{
public class Program
{
public static void Main(string[] args)
{
var logFactory = new LoggerFactory()
.AddConsole(LogLevel.Debug)
.AddDebug();
var logger = logFactory.CreateLogger<Type>();
logger.LogInformation("this is debug log");
}
}
}
Kudos to https://askguanyu.wordpress.com/2016/09/26/net-core-101-e06-net-core-logging/
4 Comments
Maxim
@anserk Don't think that's possible, since ILogger instances are generically typed (i.e.
ILogger<Startup>).
J.D. Mallen
This no longer works for .NET Core 3.1 and up.
Nashmár
See @RickAndMSFT answer below for .Net 6. You can access Logger directly via
Builder.WebApplication.Logger now.This is how I managed to get the ILogger interface configured in Startup.cs (in my case Log4Net) working when inside Program.cs:
public static void Main(string[] args)
{
var host = BuildWebHost(args);
ILogger logger = host.Services.GetService<ILogger<Program>>();
try
{
logger.LogInformation("Starting web host");
host.Run();
}
catch (Exception ex)
{
logger.LogCritical(ex, "Starting web host failed.");
}
}
- Add
using Microsoft.Extensions.DependencyInjection;so that the generic type inGetServiceworks as expected.
answered May 24, 2018 at 18:36
Leniel Maccaferri
103k48 gold badges380 silver badges495 bronze badges
1 Comment
Brent
Oddly enough, while I can get the logger inside the catch to work with NLog, I can't with Serilog. I've even created a new LoggerConfiguration() and called .CreateLogger() on it, and set it up just like I do before the try, and it won't log to serilog in the catch. The logger statement in the try logs correctly, as do all of the other places I log in other classes.
See the official doc Log in Program.cs
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.Logger.LogInformation("Adding Routes");
app.MapGet("/", () => "Hello World!");
app.Logger.LogInformation("Starting the app");
app.Run();
2 Comments
skan
But how to use the logger before the application is built?
andrew.fox
before app is built the logging is configured so it doesn't exist. You can use std Console.WriteLine() or bootstrap serilog.
New in .NET Core 6 (I have no idea if this was new to .NET core 6, 5 or 3).
var logger = LoggerFactory.Create(config =>
{
config.AddConsole();
config.AddConfiguration(builder.Configuration.GetSection("Logging"));
}).CreateLogger("Program");
This was my simple starting point, you don't actually have to pickup the Configuration section for logging, but I figured it makes sense. But you do need to specify an output; Console, although default for DI is not assumed in the factory.
Comments
What worked for me in combination with serilog based on the default template of Program.cs (.NET 6.0), was nearly the same approach as the one of Leniel Maccaferri.
ILogger logger = builder.Services.BuildServiceProvider().GetRequiredService<ILogger<Program>>();
logger.LogInformation("This is a testlog");
3 Comments
NickG
Where does "builder" come from and what is its type?
Kraego
@NickG see official documentation: learn.microsoft.com/en-us/aspnet/core/fundamentals/logging/… - 'WebApplication.CreateBuilder'
مهدی
in .Net 8 rc2 worked
Following helped me to add logger for program.cs as well as for any of the static classes
private static void TemporaryLogger(string methodName, string lineNumber)
{
var loggerFactory = LoggerFactory.Create(builder => builder.AddConsole());
var logger = loggerFactory.CreateLogger(string.Empty);
logger.LogInformation($"Test Logger for class className: Identifier - {methodName} : Line number - {lineNumber}");
}
1 Comment
Eric Erhardt
This approach has some performance issues. Calling
LoggerFactory.Create every time you want to log is wasting cycles because under the covers it uses DI to create an ILogger, and then just throws it away after logging a single message. It would be better to only do it once and cache the ILogger instance.Program.cs
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Log4Net.AspNetCore;
var builder = WebApplication.CreateBuilder(args);
builder.Logging.AddLog4Net();
Above worked for me in .net 6
Thanks to: https://onloupe.com/blog/does-log4net-work-on-net6/
