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。
