Random类，ArrayList实现随机数不重复！在线等答案！

[peng2739956]

我做了个英语默写器 实现了一个 随机显示的单词或者解释不重复的功能 但是有问题 大家帮忙看看 哪里需要改。。
在线等答案！！！

namespace 单词背诵
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        string[] words;        
        private void button2_Click(object sender, EventArgs e)
        {
            textBox1.Text = "";
            textBox2.Text = "";
            button1.Enabled = true;
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
               words= File.ReadAllLines(openFileDialog1.FileName,Encoding.Default);               
            }            
        }
        int i=0;
        string[] str3;
        string str1,str2;
        Random rn=new Random();
        ArrayList list = new ArrayList();
        private void button1_Click(object sender, EventArgs e)
        {            
            try
            {
                list.Add(s);
                Word(s);
            }
            catch 
            {
                MessageBox.Show("请选择词库");
            }
        }
        private void Word(int str)
        {            
            str3 = words[str].Split('[');
            str1 = str3[0].ToString();
            str2 = str3[1].ToString();
            button1.Enabled = false;
            textBox2.Focus();
            if (s % 2 == 0)
            {
                i = 1;
                textBox1.Text = str2;
                return;
            }
            if (s % 2 != 0)
            {
                i = 2;
                textBox1.Text = str1;
                return;
            }
        }
        int s = 0;
        private int List()
        {
           s = rn.Next(0, words.Length - 1);
           return s;
        }
        int p1, p2;
        private void button3_Click(object sender, EventArgs e)
        {
            switch (i)
            {
                case 1:
                    if (str1 == textBox2.Text.Trim())
                    {                        
                        p1 = List();                        
                        if (list.Contains(p1))
                        {
                            p2 = List();
                        }
                        if (list.Contains(p1) == false)
                        {
                            list.Add(p1);
                            textBox1.Clear();
                            textBox2.Clear();
                            Word(p1);
                        }                                              
                        return;
                    }
                    if (str1 != textBox2.Text.Trim())
                    {
                        textBox2.Text = "";
                        MessageBox.Show("回答错误");
                        return;
                    }
                    break;
                case 2:
                    if (str2.Contains(textBox2.Text.Trim()))
                    {
                        
                        p1 = List();
                        if (list.Contains(p1))
                        {
                            p2 = List();
                        }
                        if (list.Contains(p1) == false)
                        {
                            list.Add(p1);
                            textBox1.Clear();
                            textBox2.Clear();
                            Word(p1);
                        }        
                        return;
                    }
                    if (!str2.Contains(textBox2.Text.Trim()))
                    {
                        textBox2.Text = "";
                        MessageBox.Show("回答错误");
                        return;
                    }
                    break;
            }
            foreach (int[] sr in list)
            {
                if (sr.Length == words.Length)
                {
                    MessageBox.Show("此单词库的单词全部默写完毕");
                }
            }
        }
        private void textBox2_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 13)
            {
                button3_Click(null, null);
            }
        }