C#生成用户密码

如果用户的密码丢失了，网站通常生成一个新的密码发到他的邮箱。我试着写了一个，请各位批评指正！输入的参数是：level复杂程度，length密码长度。其中密码复杂程度分为6级：0数字，1小写字母，2数字加小写字母，3数字加大小写字母，4加特殊字符，5更多特殊字符。在一个Winform里放置一个按钮，三个文本框（一个为显示结果，两个为输入参数）。        private void button1_Click(object sender, EventArgs e)
        {
            int level =Convert.ToInt32(this.textBox2.Text);
            int length = Convert.ToInt32(this.textBox3.Text);
            this.textBox1.Text = GeneratePWD(level, length);
        }
        /// <summary>
        /// Generate password for new user
        /// </summary>
        /// <param name="level">0 = digits only</param>
        /// <param name="level">1 = lowercase alphabets only</param>
        /// <param name="level">2 = num+lowercase</param>
        /// <param name="level">3 = num+lowercase+uppercase</param>
        /// <param name="level">4 = num+lowercase+uppercase+special characters(!@#$%&)</param>
        /// <param name="level">5 = more special characters</param>
        /// <param name="length">Length of password: from 3 to 12</param>
        /// <returns></returns>
        private string GeneratePWD(int level, int length)
        {
            int beginPosition = 0;
            int endPosition = 100;            if (length < 3 || length > 12) length = 8;
            switch (level)
            {
                case 0:
                    endPosition = 37;
                    break;
                case 1:
                    beginPosition = 38;
                    endPosition = 63;
                    break;
                case 2:
                    endPosition = 63;
                    break;
                case 3:
                    endPosition = 89;
                    break;
                case 4:
                    endPosition = 100;
                    break;
                default:
                    endPosition = 109;
                    break;
            }
            char[] characters ={'0','0','1','1','1','1','2','2','2','2','3','3','3','3','4','4','4','4','5','5','5','5','6','6','6','6','7','7','7','7','8','8','8','8','9','9','9','9', //37
                              'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',//63
                              'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',//89
                              '!','!','@','@','#','#','$','$','%','%','&',//100
                              '^','~','+','-','*','<','>','?','/'};//109            string result = "";
            Random rnd = new Random();
            for (int i = 0; i <length; i++) 
            {
                int str = rnd.Next(beginPosition,endPosition+1);
                result += characters[str];
            }
            return result;
        }
    }看msdn上直接把随机数存入数组，也许更方便：
http://msdn.microsoft.com/en-us/library/system.random.aspx