加权随机算法

        public class WeightedRandom
        {
            /// <summary>
            /// 带权重的随机
            /// </summary>
            /// <param name="list">原始列表</param>
            /// <param name="count">随机抽取条数</param>
            /// <returns></returns>
            public static T GetRandomList<T>(List<T> list, int count) where T : RandomObject
            {
                if (list == null || list.Count <= count || count <= 0)
                {
                    return default(T);
                }

                //计算权重总和
                int totalWeights = 0;
                for (int i = 0; i < list.Count; i++)
                {
                    totalWeights += list[i].Weight + 1;  //权重+1，防止为0情况。
                }

                //随机赋值权重
                System.Random ran = new System.Random(GetRandomSeed());  //GetRandomSeed()随机种子，防止快速频繁调用导致随机一样的问题 
                List<KeyValuePair<int, int>> wlist = new List<KeyValuePair<int, int>>();    //第一个int为list下标索引、第一个int为权重排序值
                for (int i = 0; i < list.Count; i++)
                {
                    int w = (list[i].Weight + 1) + ran.Next(0, totalWeights);   // （权重+1） + 从0到（总权重-1）的随机数
                    wlist.Add(new KeyValuePair<int, int>(i, w));
                }

                //排序
                wlist.Sort(
                    delegate (KeyValuePair<int, int> kvp1, KeyValuePair<int, int> kvp2)
                    {
                        return kvp2.Value - kvp1.Value;
                    });

                //根据实际情况取排在最前面的几个
                List<T> newList = new List<T>();
                for (int i = 0; i < count; i++)
                {
                    newList.Add(list[wlist[i].Key]);
                }

                //随机法则
                return newList[0];
            }
            /// <summary>
            /// 随机种子值
            /// </summary>
            /// <returns></returns>
            private static int GetRandomSeed()
            {
                byte[] bytes = new byte[4];
                System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
                rng.GetBytes(bytes);
                return BitConverter.ToInt32(bytes, 0);
            }
        }


        public class RandomObject
        {
            /// <summary>
            /// 权重
            /// </summary>
            public int Weight { set; get; }
        }

        public class GameItemRandomObject : RandomObject
        {
            public int item { get; set; }
        }

        static void Test6()
        {
            List<GameItemRandomObject> shuidiRanObj = new List<GameItemRandomObject>();
            shuidiRanObj.Add(new GameItemRandomObject() { item = 0, Weight = 15 });
            shuidiRanObj.Add(new GameItemRandomObject() { item = 1, Weight = 30 });
            shuidiRanObj.Add(new GameItemRandomObject() { item = 2, Weight = 1 });
            shuidiRanObj.Add(new GameItemRandomObject() { item = 3, Weight = 5 });
            shuidiRanObj.Add(new GameItemRandomObject() { item = 4, Weight = 2 });
            shuidiRanObj.Add(new GameItemRandomObject() { item = 5, Weight = 12 });
            shuidiRanObj.Add(new GameItemRandomObject() { item = 6, Weight = 6 });

            var CurItem = WeightedRandom.GetRandomList<GameItemRandomObject>(shuidiRanObj, 1);
        }