此代码可以随机生成指定长度的数字+字符的密码，可以自定义长度

 /// <summary>
     /// 生成随机数的种子
     /// </summary>
    /// <returns></returns>
     private static int getNewSeed()
     {
         byte[] rndBytes = new byte[4];
         System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
         rng.GetBytes(rndBytes);
        return BitConverter.ToInt32(rndBytes, 0);
    }     /// <summary>
    /// 生成8位随机数
    /// </summary>
    /// <param name="length"></param>
    /// <returns></returns>
    static public string GetRandomString(int len)
    {
        string s = "123456789abcdefghijklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";
        string reValue = string.Empty;
        Random rnd = new Random(getNewSeed());
        while (reValue.Length < len)
        {
            string s1 = s[rnd.Next(0, s.Length)].ToString();
            if (reValue.IndexOf(s1) == -1) reValue += s1;
        }
       return reValue;
    }