c#正则表达式，电话号码，密码字母与数字组合

public static bool IsPhoneOK(string num)
    {
        if (num.Length < 11)
        {
            return false;
        }
        //电信手机号码正则
        string dianxin = @"^1[3578][01379]\d{8}$";
        Regex regexDX = new Regex(dianxin);
        //联通手机号码正则
        string liantong = @"^1[34578][01256]\d{8}";
        Regex regexLT = new Regex(liantong);
        //移动手机号码正则
        string yidong = @"^(1[012345678]\d{8}|1[345678][012356789]\d{8})$";

        string phone = @"^1([38][0-9]|4[579]|5[0-3,5-9]|6[6]|7[0135678]|9[89])\d{8}$";
        Regex regexYD = new Regex(yidong);
        Regex phoneRe = new Regex(phone);
        if (regexDX.IsMatch(num) || regexLT.IsMatch(num) || regexYD.IsMatch(num) || phoneRe.IsMatch(num))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

Regex reg = new Regex(@"^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{6,10}$");
        return reg.IsMatch(str);