1、方法
private void Log(string LogStr)
 {
     //Trace.WriteLine(LogStr);
     StreamWriter sw = null;
     try
     {
         LogStr = DateTime.Now.ToLocalTime().ToString() + "\n" + LogStr;
         sw = new StreamWriter("C:\\Text" + DateTime.Now.ToString("yyyy-MM-dd") + ".txt", true);
         sw.WriteLine(LogStr);
     }
     catch
     {
     }
     finally
     {
         if (sw != null)
         {
             sw.Close();
         }
     }
 }
2、调用
try
{
Log("成功");
}
catch(Extech ex)
{
Log("失败:"+ex.Message);
}