试图创建一个唯一的随机数。如果数据库中存在数字，则再次生成并向数据库添加值

Question

我正在尝试创建一个唯一的随机数。如果数据库中存在随机数，则再次循环该代码块，直到找到不存在的数字。将值保存到数据库。对此的任何帮助都会很棒。谢谢。

public IHttpActionResult BookMatch(int id)
{
    Guid guid = Guid.NewGuid();

    var user = User.Identity.GetUserId();
    var getuser = db.AspNetUsers.Find(user);
    var match = db.Matches.Find(id);

    Random rnd = new Random();
    var peg = rnd.Next(match.PegRangeMin, match.PegRangeMax);

    var alreadyExists = db.Pegs.Any(x => x.MatchId == match.Id && x.PegNo == peg);

    if (alreadyExists == true)
    {
        //do something
    }

    var result = new Booked()
    {

        MatchId = id,
        BookerId = user,
        TicketNo = guid.ToString(),
        //pegNo = randompeg
    };

    db.Bookeds.Add(result);
    db.SaveChanges();

    if (result == null)
    {
        throw new Exception();
    }

    var getmatch = db.Matches.Find(id);

        var body = "<p>Email From: {0} ({1}) </p>" +
                   "<h3>Match Booking Confirmation:</h3>" +
                   "<b>Ticket Number:</b><p> {2} </p>" +
                   "<b>Venue:</b><p> {3} </p>" +
                   "<b>date and time:</b><p>{4}</p>";

        var message = new MailMessage();
        message.To.Add(new MailAddress(getuser.Email));
        message.From = new MailAddress("nicholas.mciver@Activeplan.co.uk");
        message.Subject = "Matchbooker Confirmation Email";
        message.Body = string.Format(body, getuser.GetFullName(), getuser.Email,
            result.TicketNo, getmatch.Fishery.Name, getmatch.DateTime);
        message.IsBodyHtml = true;

        using (var smtp = new SmtpClient())
        {
            smtp.Send(message);
        }

    return Ok();
}

Answer 1

最简单的方法是在while (true) 循环中进行数字生成和检查：

int peg;

while (true)
{
    peg = rnd.Next(match.PegRangeMin, match.PegRangeMax);

    var alreadyExists = db.Pegs.Any(x => x.MatchId == match.Id && x.PegNo == peg);

    if (!alreadyExists) break;
}

这并不完美，因为如果取完所有可能的数字，循环将永远不会中断。但这在实践中可能不是问题，只要 min-max 范围足够大。