如何将两个日期进行分类计算

        可能做过报表的朋友和我有同样的感受，就是老板可能会说，我要****年**月**日到****年**月**日之间各年度、各季度、各月份的销售情况比较的报表。 
        马上我们想的就是如何来划分这些时间段吧。举个例子，比如日期是从2006年3月15日到2007年3月15日，如何来划分呢？我们知道.NET有System.DateTime类，今天我们讲的就是如何来灵活的使用它，构建我们划分时间段的组件。
        当然我想我需要先讲讲我们的划分原则，如上面的时间段所示，如果我们分年度来比较，那就是从06年3月15日到06年12月31日为一段，07年1月1日到3月15日为另一段；分季度的话当然是06-3-15至06-03-31、06-04-01至06-06-30... ...以此类推，再加上07-01-01至07-03-15一共5段；分月份不用多说，也是06-03-15至06-03-31、06-04-01至06-04-30... ... 07-02-01至07-02-28、07-03-01至07-03-15，一共13段。
         好了，原则讲了，接下来就是看代码的实现了，我们这里假设销售的日期就是订单下达的日期（OrderDate）。
         我们先建一个类DateDiffObject，并让它可序列化：

[Serializable]
     public   class  DateDiffObject
     {
        public ArrayList SeperateDateByYear = new ArrayList();
        public ArrayList SeperateDateByQuarter = new ArrayList();
        public ArrayList SeperateDateByMonth = new ArrayList();

        public DateDiffObject()
        {

        }
    }

          上面三个ArrayList分别就是记录我把时间段按不同标准划分后的结果。
           然后，我们需要对用户输入进来的时间段进行各类分割了：

public  DateDiffObject GetDateDiffObject(DateTime BeginDate,DateTime EndDate)
         {
            DateDiffObject dateobj = new DateDiffObject();
                        //string[] quarter length is 12, record the quarter of each month
            string[] quarter = {"1","1","1","2","2","2","3","3","3","4","4","4"};

            if(BeginDate.Year==EndDate.Year)
            {
                //Same Year
                if(quarter[BeginDate.Month - 1] == quarter[EndDate.Month - 1])
                {
                    //Same Quarter
                    if(BeginDate.Month!=EndDate.Month)
                    {
                        //Different Month
                        for(int i=0; i<=EndDate.Month - BeginDate.Month; i++)
                        {
                            if(i==0)
                            {
                                    //Seperate the first date period
                                this.dateobj.SeperateDateByMonth.Add(" and OrderDate between '"+BeginDate.ToString("yyyy-MM-dd")+"' and '"+GetMonthLastDay(BeginDate)+"' ");
                            }
                            else if(i==EndDate.Month - BeginDate.Month)
                            {
                                    //Seperate the last date period
                                this.dateobj.SeperateDateByMonth.Add(" and OrderDate between '"+GetMonthFirstDay(EndDate)+"' and '"+EndDate.ToString("yyyy-MM-dd")+"' ");
                            }
                            else
                            {
                                    //Seperate the middle date period
                                this.dateobj.SeperateDateByMonth.Add(" and OrderDate between '"+GetMonthFirstDay(BeginDate.AddMonths(i))+"' and '"+GetMonthLastDay(BeginDate.AddMonths(i))+"' ");
                            }
                        }
                    }
                }
                else
                {
                    //Different Quarter
                    for(int j=0; j<=Convert.ToInt32(quarter[EndDate.Month - 1]) - Convert.ToInt32(quarter[BeginDate.Month - 1]); j++)
                    {
                        if(j==0)
                        {
                               //Seperate the first date period
                            this.dateobj.SeperateDateByQuarter.Add(" and OrderDate between '"+BeginDate.ToString("yyyy-MM-dd")+"' and '"+GetQuarterLastDay(BeginDate)+"' ");
                        }
                        else if(j==EndDate.Month - BeginDate.Month)
                        {
                                //Seperate the last date period
                            this.dateobj.SeperateDateByQuarter.Add(" and OrderDate between '"+GetQuarterFirstDay(EndDate)+"' and '"+EndDate.ToString("yyyy-MM-dd")+"' ");
                        }
                        else
                        {
                                //Seperate the middle date period
                            this.dateobj.SeperateDateByQuarter.Add(" and OrderDate between '"+GetQuarterFirstDay(BeginDate.AddMonths(3*j - ((BeginDate.Month - 1) % 3)))+"' and '"+GetQuarterLastDay(BeginDate.AddMonths(3*j - ((BeginDate.Month - 1) % 3)))+"' ");
                        }
                    }
                }
            }
            else
            {
                //Different Year
                for(int k=0; k<=EndDate.Year - BeginDate.Year; k++)
                {
                    if(k==0)
                    {
                            //Seperate the first date period  --- Year
                        this.dateobj.SeperateDateByYear.Add(" and OrderDate between '"+BeginDate.ToString("yyyy-MM-dd")+"' and '"+GetYearLastDay(BeginDate)+"' ");
                        DateDiffObject newdateobj = new DateDiffObject();
                        //Use itself --- Recursion Method
                        newdateobj = GetDateDiffObject(DateType,BeginDate,DateTime.Parse(GetYearLastDay(BeginDate)));
                        for(int p=0; p<newdateobj.SeperateDateByQuarter.Count;p++)
                        {
                            dateobj.SeperateDateByQuarter.Add(newdateobj.SeperateDateByQuarter[p]);
                        }
                        for(int p=0; p<newdateobj.SeperateDateByMonth.Count;p++)
                        {
                            dateobj.SeperateDateByMonth.Add(newdateobj.SeperateDateByMonth[p]);
                        }                
                    }
                    else if(k==EndDate.Year - BeginDate.Year)
                    {
                            //Seperate the last date period  --- Year
                        this.dateobj.SeperateDateByYear.Add(" and OrderDate between '"+GetYearFirstDay(EndDate)+"' and '"+EndDate.ToString("yyyy-MM-dd")+"' ");
                        DateDiffObject newdateobj = new DateDiffObject();
                        //Use itself --- Recursion Method
                        newdateobj = GetDateDiffObject(DateType,DateTime.Parse(GetYearFirstDay(EndDate)),EndDate);
                        for(int p=0; p<newdateobj.SeperateDateByQuarter.Count;p++)
                        {
                            dateobj.SeperateDateByQuarter.Add(newdateobj.SeperateDateByQuarter[p]);
                        }
                        for(int p=0; p<newdateobj.SeperateDateByMonth.Count;p++)
                        {
                            dateobj.SeperateDateByMonth.Add(newdateobj.SeperateDateByMonth[p]);
                        }        
                    }
                    else
                    {
                            //Seperate the middle date period  --- Year
                        this.dateobj.SeperateDateByYear.Add(" and OrderDate between '"+GetYearFirstDay(BeginDate.AddYears(k))+"' and '"+GetYearLastDay(BeginDate.AddYears(k))+"' ");
                        DateDiffObject newdateobj = new DateDiffObject();
                        //Use itself --- Recursion Method
                        newdateobj = GetDateDiffObject(DateType,DateTime.Parse(GetYearFirstDay(BeginDate.AddYears(k))),DateTime.Parse(GetYearLastDay(BeginDate.AddYears(k))));
                        for(int p=0; p<newdateobj.SeperateDateByQuarter.Count;p++)
                        {
                            dateobj.SeperateDateByQuarter.Add(newdateobj.SeperateDateByQuarter[p]);
                        }
                        for(int p=0; p<newdateobj.SeperateDateByMonth.Count;p++)
                        {
                            dateobj.SeperateDateByMonth.Add(newdateobj.SeperateDateByMonth[p]);
                        }        
                    }
                }
            }
            return dateobj;
        }

          以上方法是用递归算法来截取个时间段然后返回一个DateDiffObject的对象。 其实大家可以看出来填入对象中各个ArrayList的数据就是SQL语句的一段，作为我们查询数据库的条件。
          接下来就是我们在上面看到的例如GetMonthFirstDay(EndDate)，GetMonthLastDay(BeginDate.AddMonths(i))等方法的实现，大家可以从方法名里看出它们将要实现的功能，就是获得每年、每季度、每月的第一天和最后一天：

public   string  GetMonthFirstDay(DateTime date)
         {
            return date.ToString("yyyy-MM-01");
        }

         public   string  GetMonthLastDay(DateTime date)
         {
            return DateTime.Parse(date.ToString("yyyy-MM-01")).AddMonths(1).AddDays(-1).ToShortDateString();
        }

         public   string  GetQuarterFirstDay(DateTime date)
         {
            return date.AddMonths(0 - ((date.Month - 1) % 3)).ToString("yyyy-MM-01");
        }

         public   string  GetQuarterLastDay(DateTime date)
         {
            return DateTime.Parse(date.AddMonths(3 - ((date.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
        }

         public   string  GetYearFirstDay(DateTime date)
         {
            return DateTime.Parse(date.ToString("yyyy-01-01")).ToShortDateString();
        }

         public   string  GetYearLastDay(DateTime date)
         {
            return DateTime.Parse(date.ToString("yyyy-01-01")).AddYears(1).AddDays(-1).ToShortDateString();
        }

       都是用DateTime类来实现的，原理很简单，每个月的第一天当然是****-**-01，最后一天就是下个月的第一天减去一天所得到的，季度和年份也是同理，大家有兴趣可以推敲一下，这里就不再赘述了。^^
       最后，就是调用它的时候了，我们先讲它序列化为一个XML文档，存放在一个特定目录下，我们这里用一个组件来管理它：

public   class  DateDiffObjectSerialize : iDateObjectSerialize
     {
        private string strPath = "./XMLDoc/"+HttpContext.Current.Request.Cookies["UserID"].Value + "/DateDiffObject.xml";
        private DateDiffObject dateobj = new DateDiffObject();

        public DateDiffObjectSerialize()
        {

        }

        public DateDiffObjectSerialize(string Path)
        {
            this.strPath = Path;
        }

        public void SerializeDateObject(DateDiffObject dateobj)
        {
            FileInfo fi = new FileInfo(strPath);
            if(fi.Exists)
            {
                fi.Delete();
            }
            XmlSerializer s = new XmlSerializer(typeof(DateDiffObject));
            Stream stream = new FileStream(HttpContext.Current.Server.MapPath(strPath),FileMode.Create);
            s.Serialize(stream, dateobj);
            stream.Close();
        }

        public void SerializeDateObject(DateDiffObject dateobj,string FilePath)
        {
            strPath = FilePath;

            FileInfo fi = new FileInfo(strPath);
            if(fi.Exists)
            {
                fi.Delete();
            }
            XmlSerializer s = new XmlSerializer(typeof(DateDiffObject));
            Stream stream = new FileStream(HttpContext.Current.Server.MapPath(strPath),FileMode.Create);
            s.Serialize(stream, dateobj);
            stream.Close();
        }

        public DateDiffObject DeserializeDateObject()
        {
            FileStream s = File.OpenRead(HttpContext.Current.Server.MapPath(strPath));
            XmlSerializer xs = new XmlSerializer(typeof(DateDiffObject));
            dateobj = (DateDiffObject)xs.Deserialize(s);
            s.Close();
            return dateobj;
        }

        public DateDiffObject DeserializeDateObject(string FilePath)
        {
            strPath = FilePath;
            FileStream s = File.OpenRead(HttpContext.Current.Server.MapPath(strPath));
            XmlSerializer xs = new XmlSerializer(typeof(DateDiffObject));
            dateobj = (DateDiffObject)xs.Deserialize(s);
            s.Close();
            return dateobj;
        }
    }

       要调用DateDiffObject时只是需要将它反序列化出来，按需提取里面的数据，然后组装到你查询语句中就行了。
       结束语：
      至于为什么要把它进行序列化，主要是我对方便使用的考量在里面，我就碰到这样的要求，不但要看报表，还要看相应的图片显示，年度、季度、月份的比较可以随时切换，当然你也可以不讲他序列化了，这个就见仁见智吧。

转载于:https://www.cnblogs.com/Louistin/archive/2007/03/17/677568.html