遍历集合操作

for (int i = recivers.Keys.Count; i-- > 0; )
                                {
                                    if (!recivers.Values.ElementAt(i).bExist)
                                    {
                                        recivers.Remove(recivers.Keys.ElementAt(i));
                                    }
                                }

//foreach (UserDictType item in userdict.Values)
                //{
                //    if (time > item.LogoutDatetime1)
                //    {
                //        userdict.Remove(item.UserGUID1);
                //    }
                //}此代码当移除一个数据时可能会引起迭代器数据序列混乱

                for (int i = userdict.Keys.Count; i-- > 0; )
                {
                    if (time > userdict.Values.ElementAt(i).LogoutDatetime1)
                    {
                        userdict.Remove(userdict.Keys.ElementAt(i));
                    }
                }