获取日期差除去双休

主要思路：计算日期差过了几周，就用日期差除7得到周数，在判断开始日期和结束日期存在周末的情况，最终得到的结果=总日期差-周数*2-结束日期和开始日期所在周末的次数

#region 计算除去周末的日期
                            var totleWeek = AllDays / 7; //经过的周数
                            var yuDay = totleWeek % 7;
                            if (yuDay == 0) 　　//正好整周
                            {
                                days = AllDays - (totleWeek * 2);
                            }
                            else
                            {
                                var weekDay = 0;
                                var Week= 0; //多余的天数有几天是周六或者周日
                                switch (start.DayOfWeek)
                                {
                                    case DayOfWeek.Monday:
                                        weekDay = 1;
                                        break;
                                    case DayOfWeek.Tuesday:
                                        weekDay = 2;
                                        break;
                                    case DayOfWeek.Wednesday:
                                        weekDay = 3;
                                        break;
                                    case DayOfWeek.Thursday:
                                        weekDay = 4;
                                        break;
                                    case DayOfWeek.Friday:
                                        weekDay = 5;
                                        break;
                                    case DayOfWeek.Saturday:
                                        weekDay = 6;
                                        break;
                                    case DayOfWeek.Sunday:
                                        weekDay = 7;
                                        break;
                                }
                                if ((weekDay == 6 && yuDay >= 2) || (weekDay == 7 && yuDay >= 1) || (weekDay == 5 && yuDay >= 3) || (weekDay == 4 && yuDay >= 4) || (weekDay == 3 && yuDay >= 5) || (weekDay == 2 && yuDay >= 6))
                                {
                                    Week = 2;
                                }
                                if ((weekDay == 6 && yuDay < 1) || (weekDay == 7 && yuDay < 5) || (weekDay == 5 && yuDay < 2) || (weekDay == 4 && yuDay < 3) || (weekDay == 3 && yuDay < 4) || (weekDay == 2 && yuDay < 5) || (weekDay == 1 && yuDay < 6))
                                {
                                    Week = 1;
                                }
                                days = AllDays - (totleWeek * 2) - Week;
                            }
#endregion