C#隨機產生數字

   private int rep = 0;
    private string GenerateCheckCodeNum(int codeCount) //產生不重複的數字
    {

        string str = string.Empty;
        long num2 = DateTime.Now.Ticks + this.rep;
        this.rep++;
        Random random = new Random(((int)(((ulong)num2) & 0xffffffffL)) | ((int)(num2 >> this.rep)));
        for (int i = 0; i < codeCount; i++)
        {
            int num = random.Next();
            str = str + ((char)(0x30 + ((ushort)(num % 10)))).ToString();
        }
        return str;
    }