日期连贯计算

需求：从选中的日期列表中，合并日期连贯的日期，组成DateSpans对象的StartDate和EndDate属性，形成新的对象List<DateSpans>，代码和结果截图如下：

using System;
using System.Collections.Generic;
using System.Linq;

namespace CalcDateRange
{
    class Program
    {
        static void Main(string[] args)
        {
            List<DateSpans> lstDateSpans = new List<DateSpans>();

            //选中的日期列表
            List<DateTime> dates = new List<DateTime> {
                new DateTime(2017,9,2),new DateTime(2017,9,1),new DateTime(2017,9,5),new DateTime(2017,9,7)
                ,new DateTime(2017,9,8),new DateTime(2017,9,8)
            };

            //把日期按从小到大排序
            dates = dates.OrderBy(p => p.Date).ToList();

            if (dates.Count > 0)
            {
                Dictionary<DateTime, DateTime> timeSpans = new Dictionary<DateTime, DateTime>();
                DateTime previous = DateTime.MinValue;
                DateTime current = DateTime.MinValue;
                DateTime currentKey = dates[0];
                DateSpans ds = new DateSpans();

                for (int i = 0; i < dates.Count; i++)
                {
                    if (!timeSpans.ContainsKey(currentKey))
                    {
                        timeSpans.Add(currentKey, DateTime.MinValue);
                    }
                    if (i > 0)
                    {
                        previous = dates[i - 1];
                    }
                    current = dates[i];
                    if (previous != DateTime.MinValue && current.Subtract(previous).Days > 1)
                    {
                        timeSpans[currentKey] = previous;
                        currentKey = current;
                        timeSpans.Add(currentKey, DateTime.MinValue);
                    }

                    if (i == dates.Count - 1)
                    {
                        timeSpans[currentKey] = current;
                    }
                }
                if (timeSpans.Count > 0)
                {
                    foreach (var item in timeSpans)
                    {
                        ds = new DateSpans();
                        ds.StartDate = item.Key;
                        ds.EndDate = item.Value;
                        lstDateSpans.Add(ds);

                        Console.WriteLine(string.Format("Start Date:{0} End Date:{1}", item.Key.ToShortDateString(), item.Value.ToShortDateString()));
                    }
                }
            }

            Console.ReadKey();
        }

        class DateSpans
        {
            public DateTime StartDate { get; set; }
            public DateTime EndDate { get; set; }
        }
    }
}

　运行结果：