异常 错误信息 到 日志事件中

 SqlConnection con=new SqlConnection("Data Source=localhost;Initial Catalog=BookStore;");
   try
   {
    con.Open();
   }
   catch(SqlException ee)
   {
    System.Diagnostics.EventLog log=new System.Diagnostics.EventLog();
    log.Source="My Application";
    string aa=ee.ToString();
    log.WriteEntry(aa);
    if(con.State!=ConnectionState.Open)
    {
     Response.Write("链接失败！");
    }
   }
   finally
   {
    con.Close();
   }