使用log4net记录日志到数据库（含自定义属性）

日志输出自定义属性！ 特来总结一下：

一、配置文件

使用log4写入数据库就不多说了，网上方法很多，自定义字段如下

 <commandText value="INSERT INTO dbo.AppLog (dtDate,sThread,sLevel,sLogger,sMessage,sException,ip,url) VALUES (@log_date, @thread, @log_level, @logger, @message, @exception,@userIP,@url)" />

 <parameter>
 <parameterName value="@userIP" />
 <dbType value="String" />
 <size value="" />
 <layout type="NNAppServer.Common.MyLayout" >
 <conversionPattern value = "%property{userIP}"/>
 </layout>
 </parameter>

NNAppServer.Common.MyLayout  是要自定义类的命名空间

二、自定义类
新建 MyCustomer 类 ，注意命名空间和配置文件一致

 public class MyCustomer
     {
         public MyCustomer(string userIP, string url)
         {
             this._userIP = userIP;
             this._url = url;
         }

         private string _userIP;

         /// <summary>
         /// 用户IP
         /// </summary>
         public string userIP
         {
             get { return _userIP; }
             set { _userIP = value; }
         }

         private string _url;

         /// <summary>
         /// 路径
         /// </summary>
         public string url
         {
             get { return _url; }
             set { _url = value; }
         }
     }

     class MyLayout : PatternLayout
     {
         public MyLayout()
         {
             this.AddConverter("property", typeof(MyMessagePatternConverter));
         }
     }

     class MyMessagePatternConverter : PatternLayoutConverter
     {
         protected override void Convert(System.IO.TextWriter writer, log4net.Core.LoggingEvent loggingEvent)
         {
             if (Option != null)
             {
                 // Write the value for the specified key
                 WriteObject(writer, loggingEvent.Repository, LookupProperty(Option, loggingEvent));
             }
             else
             {
                 // Write all the key value pairs
                 WriteDictionary(writer, loggingEvent.Repository, loggingEvent.GetProperties());
             }
         }

         private object LookupProperty(string property, log4net.Core.LoggingEvent loggingEvent)
         {
             object propertyValue = string.Empty;

             var pi = loggingEvent.MessageObject.GetType().GetProperty(property);

             if (pi != null)
                 propertyValue = pi.GetValue(loggingEvent.MessageObject, null);

             return propertyValue;
         }

三、新建一个异常过滤器，将要获取的字段写入

public class MyExceptionAttribute : IExceptionFilter
    {
        public void OnException(ExceptionContext filterContext)
        {
            var ex = filterContext.Exception;
            var ip = Common.ComHelper.GetIP();
            string url = filterContext.HttpContext.Request.RawUrl;

            LogHelper.Error(new MyCustomer(ip, url), ex);
        }
    }

参考文档： http://www.cnblogs.com/goody9807/archive/2010/10/29/1864581.html

处理webApi： 1、自定义一个类，继承ExceptionFilterAttribute，重写OnException方法  和mvc差不多

　　　　　　 2、在 WebApiConfig.cs 文件的 Register方法里面添加  config.Filters.Add(new WebApiExceptionFilterAttribute())

https://www.cnblogs.com/landeanfen/p/5363846.html

http://blog.sina.com.cn/s/blog_72463843010195ru.html

空合并运算符【 ?? 】为右结合运算符，即操作时从右向左进行组合的