求助：文本文件定时读取问题，谢谢！

    用StreamReader的ReadLine逐行读取文本文件时，设置了每1S间隔读取一行，读取结果没问题，但执行过程不受时间控制，一下从头读到尾，让我郁闷的。本人对定时读取不熟，请各位高手指教，谢谢！主要代码如下:
    
    System.Timers.Timer t = new System.Timers.Timer(1000);
    public StreamReader sr;
    public FileStream fst;
    string sLine = "";    private void Read_Click(object sender, EventArgs e)
        {
            try
                {
                    string fileName;
                    OpenFileDialog ofd = new OpenFileDialog();
                    if (ofd.ShowDialog() == DialogResult.OK)
                    {
                        fileName = ofd.FileName;
                        fst = new FileStream(fileName, FileMode.Open, FileAccess.Read);                    }
                    else
                    {
                        MessageBox.Show("文本没打开，请正确选择！");
                    }                }
                catch (Exception ee)
                {
                    ee.Message.ToString();
                }                t.Enabled = true;
                t.Elapsed += new System.Timers.ElapsedEventHandler(t_Elapsed);//#############################达到间隔时未执行        }        private void t_Elapsed(object sender,System.Timers.ElapsedEventArgs e)
        {
             
            sr = new StreamReader(fst, System.Text.Encoding.Default);
            sLine = sr.ReadLine();
            while (sLine != null)
            {
                sLine = sr.ReadLine();
                //提取行数据
                ......            }   
             sr.Close();
             fst.Close();      
         }