小弟刚刚开始学习c#，代码如下：
 private void toolStripOpen_Click(object sender, EventArgs e)
        {
            openFileDialog1.Title="我的文档";
            openFileDialog1.InitialDirectory = @"c:\";
            string filter="文本文档(*.txt)|*.txt";
            openFileDialog1.Filter = filter;
            openFileDialog1.Multiselect = false;
            if (openFileDialog1.ShowDialog() == DialogResult.Cancel)
            {
                return;
            }
            else
            {
                frmEdit frm = new frmEdit();
                frm.MdiParent = this;
                frm.Text=openFileDialog1.FileName;
                StreamReader sr = new StreamReader(openFileDialog1.OpenFile());
                RichTextBox richTextBox1 = new RichTextBox();
                richTextBox1.Text = sr.ReadToEnd();
               
                frm.Show();
               
            }
        }
运行后读不出所要打开文件的内容！求哪位高手帮忙解答一下！！！！谢谢了 ！！