public string PrizeDraw()

        {

            //奖品以及中奖率

            const string prizeString = "奖品一:33,奖品二:30,奖品三:9,奖品四:8,奖品五:7,奖品六:6,奖品七:5,奖品八:2";

            //将中奖率*100再取整,放在数组中,并从小到大排序

            var prizeArray = prizeString.Split(',').Select(j => new { Prize = j.Split(':')[], Change = (int)(double.Parse(j.Split(':')[])* ) }).OrderBy(j => j.Change).ToArray();

            //将中奖率累加,放到字典里

            var prizeDictionary = new Dictionary<string, int>();

            for (var i = ; i < ; i++)

            {

                var allChange = ;

                for (var j = ; j <= i; j++)

                {

                    allChange += prizeArray[j].Change;

                }

                prizeDictionary.Add(prizeArray[i].Prize, allChange);

            }

            //产生一个1-10000的随机数

            var rd = new Random();

            var rdChange = rd.Next(, );

            //找第一个大于随机值的奖项

            return prizeDictionary.First(j => j.Value >= rdChange).Key;

        }