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Microsoft.Extensions.Logging.Log4Net.AspNetCore

Add the log4net.config file

Here you will found an example of how your log4net.config file should look like.

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
  <appender name="DebugAppender" type="log4net.Appender.DebugAppender" >
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level %logger - %message%newline" />
    </layout>
  </appender>
  <appender name="RollingFile" type="log4net.Appender.RollingFileAppender">
    <file value="example.log" />
     <appendToFile value="true" />
    <maximumFileSize value="100KB" />
    <maxSizeRollBackups value="2" />
    <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date %5level %logger.%method [%line] - MESSAGE: %message%newline %exception" />
    </layout>
  </appender>
  <root>
    <level value="ALL"/>
    <appender-ref ref="DebugAppender" />
    <appender-ref ref="RollingFile" />
  </root>
</log4net>

For more information about log4net configuration files, please take a look into the configuration files section on the oficial documentation for Log4Net

Basic configuration

  • Install the package or reference the project into your ASP .Net Core application.
  • Add the AddLog4Net() call into your Configure method of the Startup class.
using Microsoft.Extensions.Logging;

public class Startup
{
    //...

    public void Configure(
        IApplicationBuilder app,
        IHostingEnvironment env,
        ILoggerFactory loggerFactory)
    {
        //...

        loggerFactory.AddLog4Net(); // << Add this line
        app.UseMvc();

        //...
    }
}

Custom configuration using Log4NetProviderOptions

  • Install the package or reference the project into your ASP .Net Core 2.x application.
  • Add a new Log4NetCore section on your appsettings.json file.
{
    "Log4NetCore": {
        "Name": "Test",
        "LoggerRepository": "Fantastic",
        "OverrideCriticalLevelWith": "Critical",
        "Watch": false,
        "UseWebOrAppConfig": false,
        "PropertyOverrides": [
            {
                "XPath": "/log4net/appender[@name='RollingFile']/file",
                "Attributes": {
                    "Value": "overridedFileName.log"
                }
            },
            {
                "XPath": "/log4net/appender[@name='RollingFile']/maximumFileSize",
                "Attributes": {
                    "Value": "200KB"
                }
            },
            {
                "XPath": "/log4net/appender[@name='RollingFile']/file"
            }
        ]
    }
}
  • Reference the appsettings.json file into your configuration building at your Program class (note: you should require to install *Microsoft.Extensions.Configuration.Json package)
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

public class Program
{
    public static void Main(string[] args)
        => CreateWebHostBuilder(args).Build().Run();

    public static IWebHostBuilder CreateWebHostBuilder(string[] args)
    {
        var config = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json")
            .Build();

        return WebHost.CreateDefaultBuilder(args)
            .UseConfiguration(config)
            .UseStartup<Startup>();
    }
}
  • Add the AddLog4Net() call into your Configure method of the Startup class.
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        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)
    {
        services.AddMvc();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        // Add these lines
        var loggingOptions = this.Configuration.GetSection("Log4NetCore")
                                               .Get<Log4NetProviderOptions>();
        loggerFactory.AddLog4Net(loggingOptions);

        app.UseMvc();
    }
}

Log4NetProviderOptions 'specials' reference

Property Description Default value Notes
UseWebOrAppConfig Flag to indicate if the log4net configuration section is located on the app.config / web.config file. false Not compatible with ExternalConfigurationSetup, Watch, PropertyOverrides, Log4NetConfigFileName
ExternalConfigurationSetup Indicates to the Log4NetProvider that the log4net library have been configured outside of the extension using XmlConfigurator false Not compatible with UseWebOrAppConfig, Watch, PropertyOverrides, Log4NetConfigFileName
Watch Indicates that the log4net.config file will be opened in watch mode, aka any change will reload log4net configuration. false Not compatible with UseWebOrAppConfig,ExternalConfigurationSetup, PropertyOverrides
OverrideCriticalLevelWith Allows to setup the Critical Level message written with another Level category. empty (could be Critical) See modifying logging behaviour for more information.
PropertyOverrides Json values that allow define value replacements during the log4net initialization. null Not compatible with UseWebOrAppConfig, ExternalConfigurationSetup, Watch

Overwriting the native log4net XML configuration using Log4NetProviderOptions

Sometimes we might want to modify the value of an appender, for example, the file name of our log. This might be interesting if we want to use a different name for each environment deployed. To do this, this package includes the possibility of overwriting the information of a node or the attributes of that node using the Net Core configuration system.

To do this, you will need to do the following:

  • Add a property on your log4net configuration section named PropertyOverrides. Here, you have got an example:
{
    "Log4NetCore": {
        "Name": "Test",
        "LoggerRepository": "Fantastic",
        "OverrideCriticalLevelWith": "Critical",
        "Watch": false,
        "PropertyOverrides": [
            {
                "XPath": "/log4net/appender[@name='RollingFile']/file",
                "Attributes": {
                    "Value": "overridedFileName.log"
                }
            },
            {
                "XPath": "/log4net/appender[@name='RollingFile']/maximumFileSize",
                "Attributes": {
                    "Value": "200KB"
                }
            },
            {
                "XPath": "/log4net/appender[@name='RollingFile']/file"
            }
        ]
    }
}

As you can see, the property is an array, where you can define overri elements.

Each element on this array can be defined as an object with XPath property, which will contain the XPath expression to find the node on log4net configuration file from which we want to overwrite its information, and Attributes property, that should contain a list of all the attributes you want to overwrite. In our case, we will almost always add the attribute value, followed by the value we want that attribute to take.

The NodeContent property will contain the text to be included inside the node, removing any information that was previously on the original node.