为什么调入比较长的小说之后要么卡主，要么是乱码呀？ 怎么解决哦

我是这样写的   private void 打开电子书ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            openFileDialog1.Filter = "txt files(*.txt)|*.txt";
            openFileDialog1.ShowDialog();
            string f = openFileDialog1.FileName;
            StreamReader sr1 = new StreamReader(f);
            richTextBox1.Text = sr1.ReadToEnd();
            sr1.Close();
            
        }

文件读取的代码是什么哦？初学者

好吧 谢谢