今天要求做个log4net自定义字段到数据库，在网上找了好多例子，都运行不成功。最后找了个国外的，很简单的就解决了。

log4net它已经定义的字段有

 <commandText value="INSERT INTO xiao_log(Date,Thread,Level,Logger,Message)VALUES(@log_date, @thread, @log_level, @logger, @message)"/>

中的Date,Thread,Level,Logger,Message这个5个。

现在自定义2个字段

 <commandText value="INSERT INTO xiao_log(Date,Thread,Level,Logger,Message,UserId,UserName)VALUES(@log_date, @thread, @log_level, @logger, @message,@userid,@username)"/>

自定义字段参数声明和原有参数声明的区别

<--原有字段-->

      <parameter>

        <parameterName value="@log_level"/>

        <dbType value="String"/>

        <size value=""/>

        <layout type="log4net.Layout.PatternLayout">

          <conversionPattern value="%level"/>

        </layout>

      </parameter>

      <parameter>

        <parameterName value="@logger"/>

        <dbType value="String"/>

        <size value=""/>

        <layout type="log4net.Layout.PatternLayout">

          <conversionPattern value="%logger"/>

        </layout>

      </parameter>

      <parameter>

        <parameterName value="@message"/>

        <dbType value="String"/>

        <size value=""/>

        <layout type="log4net.Layout.PatternLayout">

          <conversionPattern value="%message"/>

        </layout>

      </parameter>

      <!--自定义字段-->

      <parameter>

        <parameterName value="@userid"/>

        <dbType value="String" />

        <size value="" />

        <layout type="log4net.Layout.PatternLayout">

          <conversionPattern value="%property{userid}" />

        </layout>

      </parameter>

      <parameter>

        <parameterName value="@username"/>

        <dbType value="String" />

        <size value="" />

        <layout type="log4net.Layout.PatternLayout">

          <conversionPattern value="%property{username}" />

        </layout>

      </parameter>

最后加上这两句话，把参数替换掉就好了

        log4net.GlobalContext.Properties["userid"] = "";

                log4net.GlobalContext.Properties["username"] = "dongsheng";

                Log.Info(ex,"");