. Net core logging system

1. The level of logging

Trace < Debug < Information < Warning < Error < Critical

• Critical： be a life-and-death matter
• Error： Unhandled error messages
• Warning： Without interrupting the application , But warning errors that still need to be investigated
• Information： When the program runs, it outputs important information , Usually of long-term value
• Debug： Development 、 During commissioning , Short term useful news
• Trace： The lowest log level , I've never used

1.1 The console program uses

• Reference package

Microsoft.Extensions.Logging
Microsoft.Extensions.Logging.Console

• Program.cs Code (.NET6 Create a console program )

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

ServiceCollection services = new();
services.AddLogging(logBulider => {
    
    logBulider.AddConsole();
    logBulider.SetMinimumLevel(LogLevel.Debug); // Set the minimum level that allows log output to Debug
});

services.AddScoped<Test1>();

using (var sp = services.BuildServiceProvider())
{
    
    var test1= sp.GetRequiredService<Test1>();
    test1.Test();
}

* newly build Test1.cs Class and write code

public class Test1
    {
    
        private readonly ILogger<Test1> logger;

        public Test1(ILogger<Test1> _logger)
        {
    
            this.logger = _logger;
        }

        public void Test()
        {
    
            logger.LogDebug(" Start database synchronization ");
            logger.LogDebug(" Successfully connected to database ");
            logger.LogWarning(" Failed to find data , Try again for the first time ");
            logger.LogWarning(" Failed to find data , Retry the second time ");
            logger.LogError(" The search for data finally failed ");
        }
    }

• Running effect
  

2. It was recorded that Windows In the event viewer under

Be careful ： Unless the program is only deployed to Windows Under the system , Otherwise, it is not recommended to log like this

• In the title 1 Slightly modified in

Reference package Microsoft.Extensions.Logging.EventLog
New code logBulider.AddEventLog();

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3. Use NLog Write text file (ASP.NET Core Case study )

• nlog.config
  Officially provided configuration file

• Program.cs

builder.Services.AddLogging(logBulider => {
    
    logBulider.AddConsole();
    //logBulider.AddEventLog();
    logBulider.AddNLog();
    logBulider.SetMinimumLevel(LogLevel.Debug); // Set the minimum level that allows log output Debug
});

• controller

public class WeatherForecastController : ControllerBase
    {
    
       private readonly IConfiguration config;

        public TestController(ILogger<TestController> logger)
        {
    
            this.logger = logger;
        }

        [HttpPost]
        public JsonResult TestLog()
        {
    
            logger.LogInformation(" test Information");
            logger.LogDebug(" test Debug");
            logger.LogError(" test Error");
            return new JsonResult("");
        }
    }

• Reference package NLog.Extensions.Logging
• Be careful nlog.config Must be in lowercase , If capitalized and deployed to Linux System , Will report a mistake
• nlog.config File attribute Set to Always copy
• Add code to the project logBulider.AddNLog();

3.1 Interpretation of configuration files

The configuration file provided by the official specifies

• internalLogFile=“c:\temp\internal-nlog-AspNetCore.txt” , If you remove c:\temp\ Is to write to the system root path by default

• rules The matching rule of is from top to bottom , As long as the conditions are met , Will be written to the log

• rules Medium name attribute , By namespace+ Class name form

• rules name=“Microsoft.*” : matching Microsoft At the beginning

• rules logger writeTo=“lifetimeConsole, ownFile-web” Can match multiple

• rules logger final=true attribute ： Once matched to , There will be no further matching

4. Use NLog Write to database (ASP.NET Core Case study )

• nlog.config To configure

	<targets>	
    		<target name="database" xsi:type="Database" connectionstring="Server=.;Initial Catalog=cxlprod;Persist Security Info=False;User ID=DemoDB;Password=sa2008;MultipleActiveResultSets=False;Encrypt=True;TrustServerCertificate=False;Connection Timeout=30;">
			<commandText>
				insert into NLogInfo([Date],[origin],[Level],[Message]) values (DATEADD(HOUR, 8, GETDATE()), @origin, @logLevel, @message);
			</commandText>
			 Source of a log 
			<parameter name="@origin" layout="${callsite}" />
			 The log level 
			<parameter name="@logLevel" layout="${level}" />
			 Log message 
			<parameter name="@message" layout="${message}" />
		</target>

		</targets>
	<rules>
		<logger name="*"  writeTo="database" />
	</rules>

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Video reference ： Yang Zhongke ,NET6 course - P31 Dependency injection

Video reference ： Yang Zhongke ,NET6 course - P45 Log system