.NET 4.7中使用NLog记录日志到数据库表

1. 首先安装必要的NuGet包

在项目中安装以下NuGet包：

• NLog

• NLog.Config (可选，用于自动生成配置文件)

• 相应的数据库提供程序（如System.Data.SqlClient for SQL Server）

Install-Package NLog
Install-Package NLog.Config
Install-Package System.Data.SqlClient

2. 配置NLog.config文件

在项目中添加或修改NLog.config文件：

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"autoReload="true"internalLogLevel="Info"internalLogFile="c:\temp\nlog-internal.log"><extensions><add assembly="NLog" /></extensions><targets><!-- 数据库目标 --><target name="database" xsi:type="Database"connectionString="YourConnectionStringHere"commandText="INSERT INTO LoginLogs(ID, LoginName, Message, CreateTime) VALUES(@ID, @LoginName, @Message, @CreateTime)"><parameter name="@ID" layout="${guid}" /><parameter name="@LoginName" layout="${event-properties:item=LoginName}" /><parameter name="@Message" layout="${message}" /><parameter name="@CreateTime" layout="${date:format=yyyy-MM-dd HH\:mm\:ss}" /></target></targets><rules><logger name="*" minlevel="Info" writeTo="database" /></rules>
</nlog>

 如果需要使用异步记录日志的话，配置如下：

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"autoReload="true"internalLogLevel="Info"internalLogFile="c:\temp\nlog-internal.log"><extensions><add assembly="NLog" /></extensions><targets async="true"> <!-- 启用全局异步 --><!-- 异步数据库目标 --><target name="asyncDatabase" xsi:type="AsyncWrapper" queueLimit="10000" overflowAction="Discard"><target xsi:type="Database"connectionString="YourConnectionStringHere"commandText="INSERT INTO LoginLogs(ID, LoginName, Message, CreateTime) VALUES(@ID, @LoginName, @Message, @CreateTime)"><parameter name="@ID" layout="${guid}" /><parameter name="@LoginName" layout="${event-properties:item=LoginName}" /><parameter name="@Message" layout="${message}" /><parameter name="@CreateTime" layout="${date:format=yyyy-MM-dd HH\:mm\:ss}" /></target></target></targets><rules><logger name="*" minlevel="Info" writeTo="asyncDatabase" /></rules>
</nlog>

3. 创建数据库表

确保你的数据库中有对应的表结构：

CREATE TABLE LoginLogs (ID UNIQUEIDENTIFIER PRIMARY KEY,LoginName NVARCHAR(100),Message NVARCHAR(MAX),CreateTime DATETIME
)

4. 在代码中使用NLog记录登录日志 

using NLog;public class LoginService
{private static readonly Logger Logger = LogManager.GetCurrentClassLogger();public void LogLoginAttempt(string loginName, string message, bool isSuccess){var logEvent = new LogEventInfo{Level = isSuccess ? LogLevel.Info : LogLevel.Warn,Message = message};logEvent.Properties["LoginName"] = loginName;Logger.Log(logEvent);}
}

5. 使用示例 

var loginService = new LoginService();// 成功登录
loginService.LogLoginAttempt("john.doe", "User logged in successfully", true);// 失败登录
loginService.LogLoginAttempt("john.doe", "Invalid password", false);