private void 打开Button_Click(object sender, EventArgs e)
        { 
            openFileDialog1.DefaultExt = "*.rtf";
            openFileDialog1.Filter = "RTF Files|*.rtf|(*.txt)|*.txt";
            openFileDialog1.FilterIndex = 2;
            openFileDialog1.RestoreDirectory = true;



            if (openFileDialog1.ShowDialog() == DialogResult.OK && openFileDialog1.FileName.Length > 0)
            {
                string filname = openFileDialog1.FileName;
                textBox1.Text=filname;
               
                
            }
        }