我用一个listbox和一个textbox组合实现边输入便提示的效果
我想问问我在textbox里的写代码合理吗，思路对吗
请指点一下


private void textBox1_TextChanged(object sender, EventArgs e)
        {
            //首先，获取textBox1的内容
            string str = textBox1.Text.Trim().ToString();
            
            //判断输入的内容（目的要排除在第一位输入空格的情况）
            if (textBox1.Text.Trim ().ToString () == "")
            {
                //如果一直输入空格将什么反应也没有（也可给出提示）
                listBox1.Visible = false;
                label.Visible = false;
                button5.Enabled = false;
            }
            //排除第一位为空格后，就要开始判断输入的字符是不是0-9这十个数字之内的
            else
            {
                //这个正则表达式判断的是：任意的一个1位到8位的字符串，是不是数字型的字符串，也就是说是不是由0-9组成的
                string ss = @"^\d{1,8}$";
                Regex reg = new Regex(ss);
                //进行判断
                if (reg.IsMatch(str))
                {
                    //判断成功后，还要判断输入的位数。学号是8位的
                    //当字符长度少于8位
                    if (textBox1.Text != "" && textBox1.Text.Length < 8)
                    {
                        //这里用的是like的查询方法，也就是虚查询 。例如，查询所有学生中，姓王的学生，肯定会查出来好多人。就是这个意思
                        jC8 jc8 = new jC8();
                        ArrayList list = jc8.xuehaoList(str);
                        listBox1.Items.Clear();
                        listBox1.Visible = true;
                        for (int i = 0; i < list.Count; i++)
                        {
                            listBox1.Items.Add(list[i].ToString());
                        }
                        label.Visible = false;
                        button5.Enabled =false ;
                    }
                    //当字符位数等于8位时，就不再用虚查询了，用那种一般就行了。（虚查询在这里用不了，因为已经到达8位）
                    if (textBox1.Text.Length == 8)
                    {
                        jC8_2_ jc8_2 = new jC8_2_();
                        if (jc8_2.xuehao(str).Trim() != "")
                        {
                            listBox1.Items.Clear();
                            listBox1.Visible = true;
                            listBox1.Items.Add(jc8_2.xuehao(str).Trim());
                            label.Visible = false;
                            label.Text = "输入正确，学号存在。";
                            label.ForeColor = Color.Green ;
                            label.Visible = true;
                            //在输入学号存在时，把这个学号存下来。这部很重要，后面的添加、修改、删除全都要它
                            vip = str;
                           
                            //这个timer1 是为了在8位学号输入正确时，能在1秒后让listBox1隐藏。
                            //我认为这一秒要有，算是给用户一个提示，提示用户，您输的学号在这里（是它）。人性吧 O(∩_∩)O哈哈~
                            timer1.Start();
                           
                            //激活button5，就是那个确定按钮
                            button5 .Enabled =true ;
                        }
                        else
                        {
                            label.Visible = true ;
                            label.ForeColor = Color.Firebrick;
                            label.Text = "输入的学号不存在！";
                            listBox1.Visible = false;
                            button5.Enabled = false;

                        }
                    }
                }
                else
                {
                    listBox1.Visible = false;
                    label.Visible = true;
                    label .Text = "输入的字符不合法！\n不是0-9这十个数字之中。";
                    label.ForeColor = Color.Firebrick;
                    button5.Enabled = false ;
                }
            }

        }