拖读取文本内容 ：  

private void richTextBox1_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
        {
            string[] s = (string[])e.Data.GetData(DataFormats.FileDrop, true);
            int i;
            for (i = 0; i < s.Length; i++)
                fileAddress = s[i];
            richTextBox1.LoadFile((string)fileAddress, RichTextBoxStreamType.PlainText);
        }