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How to attach Serilog to dotnetcore Logging framework and inject the logging service as an open-generic type

I'm trying to attach Serilog to Dotnet core logging framework in a console application. Everything works great in terms of configuration. However, I cannot somehow get the Dependency Injection to work.
For this logging approach that I'm following, each class that needs logging will have to work with ILogger field. The problem that I have is how to register ILogger service as an open-generic type(So I can pass any ILogger<>). When I run my current code I get this exception:
Open generic service type
'Microsoft.Extensions.Logging.ILogger`1[TCategoryName]' requires
registering an open generic implementation type. (Parameter
'descriptors')
I have looked at the thread over here but it seems like my problem is a bit different.
This is my code:
The "Test" is a class that needs logging functionality:
public class Test
{
private readonly ILogger _logger;
public Test(ILogger<Test> logger)
{
_logger = logger;
}
public void DoSomething()
{
//code here
_logger.LogInformation("This is the logged error");
}
}
In the Main I have something like:
var log = serviceProvider.GetService<ILogger<Test>>();
new Test(log).DoSomething();
And this is how I configure my ILogger service:
public static IServiceCollection ConfigureSerilog(this IServiceCollection services)
{
var logger = new LoggerConfiguration()
.MinimumLevel.Debug()
.MinimumLevel.Override("Microsoft", Serilog.Events.LogEventLevel.Warning)
.WriteTo.Console(restrictedToMinimumLevel: Serilog.Events.LogEventLevel.Information)
.WriteTo.File(#"Logs\orgManager.log", rollingInterval: RollingInterval.Day)
.WriteTo.Sink(new TelegramSink(), LogEventLevel.Error)
.CreateLogger();
ApplicationLogging.LoggerFactory.AddSerilog(logger);
services.AddSingleton(typeof(ILogger<>), s => ApplicationLogging.CreateLogger(typeof(ILogger<>)));
return services;
}
This is the ApplocationLogging class(accessible throughout the application):
public static class ApplicationLogging
{
public static ILoggerFactory LoggerFactory { get; } = new LoggerFactory();
public static ILogger CreateLogger(Type t)
{
return LoggerFactory.CreateLogger(t);
}
}

unable to inject dependency in .net core 3.1

Hi i am following microsoft docs ...
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-3.1#json-configuration-provider
in order to inject configurations as singleton in .NET Core Web API
Here is Program.cs code where i load my configurations:
public class Program
{
public static Dictionary<string, string> arrayDict =
new Dictionary<string, string>
{
{"connString", "Data Source =xxx/xxx;User Id =xxx;Password =xxx"}
};
public static void Main(string[] args)
{
CreateHostBuilder(args).Build().Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureAppConfiguration(builder =>
{
builder.AddInMemoryCollection(arrayDict);
builder.AddJsonFile(
"appsettings.json", optional: false, reloadOnChange: false);
})
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
Here in Startup.cs i use following
public class Startup
{
private readonly IConfiguration Configuration;
public Startup(IConfiguration config)
{
Configuration = config;
}
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
services.AddSingleton<IConfiguration>(Configuration);
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseHttpsRedirection();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}
}
Still when i am using dependency injection in my Controller i am unable to inject IConfiguration, and get following error at invoking cotroller action (runtime error):
A suitable constructor for type 'IrisDotNetCore.Controllers.LoginController' could not be located. Ensure the type is concrete and services are registered for all parameters of a public constructor.
LoginController.cs Code:
[Route("api/[controller]")]
[ApiController]
public class LoginController : ControllerBase
{
IConfiguration _configuration;
LoginController(IConfiguration configuration)
{
_configuration = configuration;
}
}
What is possibly wrong here?

Your constructor has to be public or internal - remember that in your situation the instance of the LoginController can't be created (because LoginController method is private). Even the error message (Ensure the type is concrete and services are registered for all parameters of a public constructor) suggests this.

Get instance of singleton service in startup

I have the following situation:
startup.cs
services.AddSingleton<IConfigurationManager, ConfigurationManager>();
ConfigurationManager configurationManager = new ConfigurationManager();
services.AddDbContext<MyContext>(options =>
options.UseSqlServer(configurationManager.DatabaseConnectionString));
So, in order to create my context I need the connection string which this configurationManager provides to me. However, I would still like to keep the ConfigurationManager as a service.
Is there a way to do this without explicitly instantiating the configurationManager or is it perhaps even fine to leave it like this?

It's possible to access the IServiceProvider while building the context:
services.AddDbContext<MyContext>((serviceProvider, options) =>
{
var configManager = serviceProvider.GetService<IConfigurationManager>();
options.UseSqlServer(configManager.DatabaseConnectionString);
});
However, here your best options might be to read the Iconfiguration injected in Startup.cs:
public class Startup
{
public IConfiguration Configuration { get; }
public IHostingEnvironment HostingEnvironment { get; }
public Startup(IConfiguration configuration, IHostingEnvironment env)
{
Configuration = configuration;
HostingEnvironment = env;
}
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<MyContext>(options =>
{
options.UseSqlServer(Configuration.GetConnectionString("MyContext"));
});
}
}

You can use the service provider to get instances of services:
Build the services provider -
var provider = services.BuildServiceProvider();
Get specific service -
provider.GetService<T>();
Although a better option would be to use the IConfiguration .NET Core provides - https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-3.1
Using this method you can set IConfiguration to parse your config settings in the Startup method. From there you can then inject these settings into the required classes.

Also you can do sth similar to this.
I am not familiar with what you do with your configuration manager to provide a precise answer.
Basically you can do a pre-config inside your Program.cs.
Build your configuration here. As you can see i am passing IConfigurationBuilder.
Program.cs
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.ConfigureAppConfiguration(AddDbConfiguration)
.UseStartup<Startup>();
private static void AddDbConfiguration(WebHostBuilderContext context, IConfigurationBuilder builder)
{
var configuration = builder.Build(); // you could instantiate you Configuration manager here and append to the configuration.
var connectionString = configuration.GetConnectionString("Database");
builder.AddDemoDbProvider(options => options.UseSqlServer(connectionString));
}
source: https://medium.com/#dneimke/custom-configuration-in-net-core-2-193ff6f02046

Custom Logger Provider being excluded by Serilog

Serilog works great, but I noticed it seems to exclude any custom logger providers I setup.
When I have UseSerilog() in my Startup, my CustomProvider never gets created (CreateLogger never gets called).
Is it possible to still use custom providers with Serilog?
//class Program, Main Method
WebHost.CreateDefaultBuilder(args)
.UseConfiguration(config)
.UseSerilog() //after adding this, my Custom Logger never gets called
.UseStartup<Startup>()
.Build();
//class Startup
public void Configure(IApplicationBuilder app, ILoggerFactory logger, IServiceProvider serviceProvider)
{
logger.AddProvider(new CustomProvider(serviceProvider));
}
public class CustomProvider : ILoggerProvider
{
private readonly IServiceProvider _serviceProvider;
public void Dispose()
{
}
public CustomProvider(IServiceProvider serviceProvider)
{
_serviceProvider = serviceProvider;
}
//--------------never gets called---------------
public ILogger CreateLogger(string categoryName)
{
var logger = _serviceProvider.GetService<CustomLogger>();
logger.LogLevel = LogLevel.Error;
return logger;
}
}

You'll need to plug your custom provider into Serilog (as a sink) instead. Serilog replaces the entire default logging pipeline for greater efficiency and so that there aren't two sets of level controls and filters to keep in sync.
This post has the background: https://nblumhardt.com/2017/08/use-serilog/.

How do I write logs from within Startup.cs?

In order to debug a .NET Core app which is failing on startup, I would like to write logs from within the startup.cs file. I have logging setup within the file that can be used in the rest of the app outside the startup.cs file, but not sure how to write logs from within the startup.cs file itself.

.Net Core 3.1
Unfortunately, for ASP.NET Core 3.0, the situation is again a bit different. The default templates use the HostBuilder (instead of the WebHostBuilder) which sets up a new generic host that can host several different applications, not limited to web applications. Part of this new host is also the removal of the second dependency injection container that previously existed for the web host. This ultimately means that you won’t be able to inject any dependencies apart from the IConfiguration into the Startup class. So you won’t be able to log during the ConfigureServices method. You can, however, inject the logger into the Configure method and log there:
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILogger<Startup> logger)
{
logger.LogInformation("Configure called");
// …
}
If you absolutely need to log within ConfigureServices, then you can continue to use the WebHostBuilder which will create the legacy WebHost that can inject the logger into the Startup class. Note that it’s likely that the web host will be removed at some point in the future. So you should try to find a solution that works for you without having to log within ConfigureServices.
.NET Core 2.x
This has changed significantly with the release of ASP.NET Core 2.0. In ASP.NET Core 2.x, logging is created at the host builder. This means that logging is available through DI by default and can be injected into the Startup class:
public class Startup
{
private readonly ILogger<Startup> _logger;
public IConfiguration Configuration { get; }
public Startup(ILogger<Startup> logger, IConfiguration configuration)
{
_logger = logger;
Configuration = configuration;
}
public void ConfigureServices(IServiceCollection services)
{
_logger.LogInformation("ConfigureServices called");
// …
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
_logger.LogInformation("Configure called");
// …
}
}

Option 1: Directly use log (e.g. Serilog) in startup-
public class Startup
{
public Startup(IHostingEnvironment env)
{
Log.Logger = new LoggerConfiguration()
.MinimumLevel.Debug()
.WriteTo.RollingFile(Path.Combine(env.ContentRootPath, "Serilog-{Date}.txt"))
.CreateLogger();
Log.Information("Inside Startup ctor");
....
}
public void ConfigureServices(IServiceCollection services)
{
Log.Information("ConfigureServices");
....
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
Log.Information("Configure");
....
}
Output:
To setup Serilog in asp.net-core application, check out the Serilog.AspNetCore package on GitHub.
Option2: Configure logging in program.cs like this-
var host = new WebHostBuilder()
.UseKestrel()
.ConfigureServices(s => {
s.AddSingleton<IFormatter, LowercaseFormatter>();
})
.ConfigureLogging(f => f.AddConsole(LogLevel.Debug))
.UseStartup<Startup>()
.Build();
host.Run();
User loggerFactory in startup like this-
public class Startup
{
ILogger _logger;
IFormatter _formatter;
public Startup(ILoggerFactory loggerFactory, IFormatter formatter)
{
_logger = loggerFactory.CreateLogger<Startup>();
_formatter = formatter;
}
public void ConfigureServices(IServiceCollection services)
{
_logger.LogDebug($"Total Services Initially: {services.Count}");
// register services
//services.AddSingleton<IFoo, Foo>();
}
public void Configure(IApplicationBuilder app, IFormatter formatter)
{
// note: can request IFormatter here as well as via constructor
_logger.LogDebug("Configure() started...");
app.Run(async (context) => await context.Response.WriteAsync(_formatter.Format("Hi!")));
_logger.LogDebug("Configure() complete.");
}
}
Complete details available on this link

In .NET Core 3.1, you can create a logger directly using LogFactory.
var loggerFactory = LoggerFactory.Create(builder =>
{
builder.AddConsole();
});
ILogger logger = loggerFactory.CreateLogger<Startup>();
logger.LogInformation("Example log message");

The official solution is currently to setup a local LoggerFactory like this:
using var loggerFactory = LoggerFactory.Create(builder =>
{
builder.SetMinimumLevel(LogLevel.Information);
builder.AddConsole();
builder.AddEventSourceLogger();
});
var logger = loggerFactory.CreateLogger("Startup");
logger.LogInformation("Hello World");
See also: https://github.com/dotnet/aspnetcore/issues/9337#issuecomment-539859667

For .Net 6
var builder = WebApplication.CreateBuilder(args);
...
var app = builder.Build();
var logger = ((IApplicationBuilder)app).ApplicationServices.GetService<ILogger<Program>>();
logger.LogInformation("Some logs");
Or even more easy way:
var builder = WebApplication.CreateBuilder(args);
...
var app = builder.Build();
ILogger logger = app.Logger;

Using Rolf's answer, I put this in my Startup constructor:
private readonly ILogger _logger;
public Startup(IConfiguration configuration)
{
Configuration = configuration;
using var loggerFactory = LoggerFactory.Create(builder =>
{
builder.SetMinimumLevel(LogLevel.Information);
builder.AddConsole();
builder.AddEventSourceLogger();
});
_logger = loggerFactory.CreateLogger<Startup>();
}
public void ConfigureServices(IServiceCollection services)
{
_logger.LogInformation("ConfigureServices...");
// ...and so on...
}

For .NET Core 3.0 the official docs has this to say: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/logging/?view=aspnetcore-3.0#create-logs-in-startup
Writing logs before completion of the DI container setup in the Startup.ConfigureServices method is not supported:
Logger injection into the Startup constructor is not supported.
Logger injection into the Startup.ConfigureServices method signature is not supported
But as they say in the docs you can configure a service that depends on ILogger, so if you wrote a class StartupLogger:
public class StartupLogger
{
private readonly ILogger _logger;
public StartupLogger(ILogger<StartupLogger> logger)
{
_logger = logger;
}
public void Log(string message)
{
_logger.LogInformation(message);
}
}
Then in Startup.ConfigureServices add the service, then you need to build the service provider to get access to the DI container:
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton(provider =>
{
var service = provider.GetRequiredService<ILogger<StartupLogger>>();
return new StartupLogger(service);
});
var logger = services.BuildServiceProvider().GetRequiredService<StartupLogger>();
logger.Log("Startup.ConfigureServices called");
}
Edit: this produces a compiler warning, for the sake of debugging your StartUp class this should be OK but not for production:
Startup.cs(39, 32): [ASP0000] Calling 'BuildServiceProvider' from application code results in an additional copy of singleton services being created. Consider alternatives such as dependency injecting services as parameters to 'Configure'.

None of the existing answers worked for me. I'm using NLog, and even building a new ServiceCollection, calling .CreateBuilder() on any service collection, creating a logging service ... none of that would write to a log file during ConfigureServices.
The problem is that logging isn't really a thing until after the ServiceCollection is built, and it's not built during ConfigureServices.
Basically, I just want (need) to log what's going on during startup in a configuration extension method, because the only tier I'm having a problem on is PROD, where I can't attach a debugger.
The solution that worked for me was using the old .NET Framework NLog method:
private static readonly NLog.Logger Logger = NLog.LogManager.GetCurrentClassLogger();
Added that right to the extension method class, and I was able to write to a log ("the" log) during ConfigureServices and after.
I have no idea if this is a good idea to actually release into production code (I don't know if the .NET controlled ILogger and this NLog.ILogger will conflict at any point), but I only needed it to see what was going on.

I use a solution avoiding 3rd party loggers implementing a "logger buffer" with ILogger interface.
public class LoggerBuffered : ILogger
{
class Entry
{
public LogLevel _logLevel;
public EventId _eventId;
public string _message;
}
LogLevel _minLogLevel;
List<Entry> _buffer;
public LoggerBuffered(LogLevel minLogLevel)
{
_minLogLevel = minLogLevel;
_buffer = new List<Entry>();
}
public IDisposable BeginScope<TState>(TState state)
{
return null;
}
public bool IsEnabled(LogLevel logLevel)
{
return logLevel >= _minLogLevel;
}
public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
{
if (IsEnabled(logLevel)) {
var str = formatter(state, exception);
_buffer.Add(new Entry { _logLevel = logLevel, _eventId = eventId, _message = str });
}
}
public void CopyToLogger (ILogger logger)
{
foreach (var entry in _buffer)
{
logger.Log(entry._logLevel, entry._eventId, entry._message);
}
_buffer.Clear();
}
}
Usage in startup.cs is easy, of course you get log output after call of Configure. But better than nothing. :
public class Startup
{
ILogger _logger;
public Startup(IConfiguration configuration, IWebHostEnvironment env)
{
_logger = new LoggerBuffered(LogLevel.Debug);
_logger.LogInformation($"Create Startup {env.ApplicationName} - {env.EnvironmentName}");
}
public void ConfigureServices(IServiceCollection services)
{
_logger.LogInformation("ConfigureServices");
services.AddControllersWithViews();
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<Startup> logger)
{
(_logger as LoggerBuffered).CopyToLogger(logger);
_logger = logger; // Replace buffered by "real" logger
_logger.LogInformation("Configure");
if (env.IsDevelopment())

Main code:
public class Program
{
public static void Main(string[] args)
{
BuildWebHost(args).Run();
}
public static IWebHost BuildWebHost(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>()
.Build();
}
CreateDefaultBuilder sets up a default console logger.
... configures the ILoggerFactory to log to the console and debug output
Startup code:
using Microsoft.Extensions.Logging;
...
public class Startup
{
private readonly ILogger _logger;
public Startup(IConfiguration configuration, ILoggerFactory logFactory)
{
_logger = logFactory.CreateLogger<Startup>();
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
_logger.LogInformation("hello stackoverflow");
}
I couldn't get the injection of an ILogger to work, but perhaps that's because it's not a controller. More info welcome!
Refs:
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/logging/?view=aspnetcore-2.1&tabs=aspnetcore2x

Are you making decisions about which services you are using at runtime that you wish to log? Or are you making decisions about how those services are configured, which you wish to log?
In other words;
public void ConfigureServices(IServiceCollection services){
// Do you really want to log something here?
services.AddRazorPages(options => {
// Or would you be satisfied by logging something here?
});
}
If it is only the latter, you can move the implementation of these lambda functions into an IConfigureOptions<T> service, allowing you to inject other services. Continuing the above example, you could create the following;
public class ConfigureRazorPagesOptions : IConfigureOptions<RazorPagesOptions>
{
private readonly ILogger<ConfigureRazorPagesOptions> logger;
public ConfigureRazorPagesOptions(ILogger<ConfigureRazorPagesOptions> logger)
{
this.logger = logger;
}
public void Configure(RazorPagesOptions options)
{
logger.LogInformation("Now I can log here!");
}
}
public void ConfigureServices(IServiceCollection services){
services.AddRazorPages();
services.AddSingleton<IConfigureOptions<RazorPagesOptions>, ConfigureRazorPagesOptions>();
}
If your .ConfigureServices method is getting too complicated, you might want to create such services. However, that's a lot of boilerplate to add for each options type. There is also an equivalent shorthand, to inject other services into a configuration lamda;
services.AddOptions<RazorPagesOptions>()
.Configure<ILogger<RazorPagesOptions>>((options, logger) => {
logger.LogInformation("I can log here too!");
});

This worked for me
private static readonly Logger logger = LogManager.GetLogger("Audit")

I found a very easy implementation:
public void ConfigureServices(IServiceCollection services)
{
services.AddControllersWithViews();
var conn = Configuration.GetValue("conn", Configuration.GetConnectionString("Conn"));
Console.WriteLine($#"System starting at {DateTime.Now}");
Console.WriteLine($#"Database: {conn}");
}
Just using Console.WriteLine worked, even on Docker.

Just use the line below for logging in Startup.cs
Log.Information("App started.");