c# 用ELMAH日志组件处理异常

protected void Application_Error(object sender, EventArgs e)
    {
      if (BQoolCommon.Helpers.Setting.CommonSetting.IsProd())
      {
        if (e is ExceptionFilterEventArgs exceptionFilter)
        {
          if (exceptionFilter.Exception is HttpException httpException && httpException.Message.StartsWith(_exceptionMsg))
          {
            Response.Redirect("/");
          }
        }
        Response.Clear();
        Server.ClearError();
        Response.StatusCode = 404;
      }
    }

public void ErrorMail_Filtering(object sender, ExceptionFilterEventArgs e)
    {
      if (e.Exception is HttpException httpException && (httpException.GetHttpCode() == 404 || httpException.Message.StartsWith(_exceptionMsg)))
      {
        e.Dismiss();
      }
    }

void ErrorMail_Mailing(object sender, Elmah.ErrorMailEventArgs e)
    {
      string machineName = "none server";
      try
      {
        if (Request != null)
        {
          machineName = Request.ServerVariables["HTTP_HOST"];
        }
      }
      catch
      {
      }

      // 取得 Elamh ErrorMail 的主旨
      // "$MachineName$ at $ErrorTime$ : {0}"
      string elmahSubject = e.Mail.Subject;
      //替換 ErrorMail 的主旨內容
      string emailSubject = string.Format("BigCRM.Web Error => {0}",
        elmahSubject
          .Replace("$MachineName$", machineName)
      );

      e.Mail.Subject = emailSubject;
    }

<elmah>
  <!--
    See http://code.google.com/p/elmah/wiki/SecuringErrorLogPages for 
    more information on remote access and securing ELMAH.
  -->
  <security allowRemoteAccess="false"/>
 </elmah>
 <location path="elmah.axd" inheritInChildApplications="false">
  <system.web>
   <httpHandlers>
    <add verb="POST,GET,HEAD" path="elmah.axd" type="Elmah.ErrorLogPageFactory, Elmah"/>
   </httpHandlers>
   <!-- 
    See http://code.google.com/p/elmah/wiki/SecuringErrorLogPages for 
    more information on using ASP.NET authorization securing ELMAH.

   <authorization>
    <allow roles="admin" />
    <deny users="*" /> 
   </authorization>
   -->
  </system.web>
  <system.webServer>
   <handlers>
    <add name="ELMAH" verb="POST,GET,HEAD" path="elmah.axd" type="Elmah.ErrorLogPageFactory, Elmah" preCondition="integratedMode"/>
   </handlers>
  </system.webServer>
 </location>