读取文本行

    public static string gettextbyline(int line)
        {

            StreamReader sr = new StreamReader("connectionString.do", Encoding.GetEncoding("GB2312"));
            String strline;
            TextBox textBox1 = new TextBox();
            while ((strline = sr.ReadLine()) != null)
            {
                textBox1.Text += strline.ToString() + "\r\n";

            }
            return textBox1.Lines[line - 1].ToString();
        }