Net中有一個(gè)DateTime結(jié)構(gòu)類(lèi)，涉及時(shí)間和日期，這個(gè)類(lèi)大量使用?？墒?，他的名稱(chēng)已經(jīng)顯著的表明他是表達(dá)某個(gè)具體的時(shí)刻。當(dāng)我們不需要每天的具體時(shí)間時(shí)，如：我的程序邏輯僅僅需要年月（發(fā)工資的周期？），這個(gè)DateTime顯得有些累贅，甚至不合用。
一般人們解決的方式，仍然使用DateTime而從數(shù)據(jù)上，設(shè)置hour,mintue等等為0。 然而，這與DDD的理念相背，名稱(chēng)有與含義有偏差，另外，數(shù)據(jù)一致性的維護(hù)，散布在各個(gè)角落，如，保證日期始終為1，小時(shí)，分鐘為0。另外，與月份相關(guān)的功能，如：得到下一個(gè)月份，要么用DateTime本身的功能（AddMonths),要么提煉出一個(gè)Utitlies出來(lái)。 前者，需要開(kāi)發(fā)者時(shí)刻重復(fù)DateTime到Y(jié)earMonth的映射邏輯，后者是個(gè)反模式。 （本文版權(quán)屬于? 2012 - 2013 予沁安）

這里，我創(chuàng)建出一個(gè)基本類(lèi)型YearMonth，可以作為代碼的基本磚塊。

[代碼] 用Extension的方式，來(lái)增強(qiáng)代碼流暢性和可讀性

 public static class YearMonthExtension
    {
        public static YearMonth year(this int year, int month)
        {
            return new YearMonth(year, month);
        }

        public static bool is_later_than(this YearMonth left, YearMonth right) {
            return left.CompareTo(right) > 0;
        }

        public static bool is_ealier_than(this YearMonth left, YearMonth right) {
            return left.CompareTo(right) < 0;
        }

        public static YearMonth get_ealier(this YearMonth left, YearMonth right)
        {
            if (left.is_ealier_than(right))
                return left;
            return right;
        }

        public static YearMonth get_later(this YearMonth left, YearMonth right)
        {
            if (left.is_later_than(right))
                return left;
            return right;
        }
}

[代碼] 從測(cè)試看功能：公用的測(cè)試基類(lèi)，很簡(jiǎn)單，就是聲明一個(gè)YearMonth對(duì)象做測(cè)試

public class YearMonthSpecs
    {
        protected static YearMonth subject;

    }

[代碼] 通過(guò)構(gòu)造器，創(chuàng)建YearMonth對(duì)象

public class When_init_by_year_month
        :YearMonthSpecs
    {
        private Because of =
            () => subject = new YearMonth(2011,3);

        private It year_should_set_properly =
            () => subject.Year.ShouldEqual(2011);

         private It month_should_set_properly =
             () => subject.Month.ShouldEqual(3);

    }

[代碼] 通過(guò)流暢接口創(chuàng)建YearMonth: 2012.year(3)。你還可以自己定制為: 2012.年(3)

public class When_create_year_month_through_fluent_interface
    {
        private It should_create_year_month_properly =
            () => 2012.year(3).ShouldEqual(new YearMonth(2012, 3));
    }

[代碼] 通過(guò)字符串創(chuàng)建

public class When_init_by_string : YearMonthSpecs
    {
        private Because of =
            () => subject = new YearMonth("2011年01月");

        private It year_should_set_properly =
             () =>
                 {
                     subject.Year.ShouldEqual(2011);
                     subject.Month.ShouldEqual(1);
                 };
    }

private It far_past_last_month_is_still_far_past =
            () => YearMonth.FarPast.get_last().ShouldEqual(YearMonth.FarPast);
        private It far_past_next_month_is_still_far_past =
         () => YearMonth.FarPast.get_next().ShouldEqual(YearMonth.FarPast);

        private It far_future_last_month_is_stil_far_future =
          () => YearMonth.FarFuture.get_last().ShouldEqual(YearMonth.FarFuture);

        private It far_future_next_month_is_stil_far_future =
            () => YearMonth.FarFuture.get_next().ShouldEqual(YearMonth.FarFuture);

YearMonth結(jié)構(gòu)類(lèi)型的完整代碼

using System;
using Skight.Arch.Domain.Interfaces;

namespace Skight.Arch.Domain.Entities
{
    public struct YearMonth : IEquatable<YearMonth>, IComparable<YearMonth>
    {
        private readonly int ticks;
        private readonly int year;
        private readonly int month;
        private const int MONTHS_PER_YEAR=12;

        public static YearMonth FarPast = new YearMonth(0,1);
        public static YearMonth FarFuture = new YearMonth(9999,12);
        #region Constructors by ticks, year/month and datetime
        internal YearMonth(int ticks)
        {
            this.ticks = ticks;
            int remain;
            year = Math.DivRem(ticks-1, MONTHS_PER_YEAR, out remain);
            month = remain + 1;
        }
        public YearMonth(int year, int month)
            :this(year*MONTHS_PER_YEAR + month){}
        public YearMonth(DateTime date_time)
            :this(date_time.Year,date_time.Month){}

        public YearMonth(string yearMonth):this(int.Parse(yearMonth.Substring(0, 4))
            ,int.Parse(yearMonth.Substring(5, 2)))
        {}

        #endregion 

        public int Year { get { return year; } }
        public int Month { get { return month; } }
        public DateTime as_date_Time()
        {
            return new DateTime(Year,Month,1);
        }

        public override string ToString()
        {
            return string.Format("{0}年{1}月", year.ToString("0000"), month.ToString("00"));
        }

        #region Euqals and Compare
        public bool Equals(YearMonth other)
        {
            return other.ticks == ticks;
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj)) return false;
            if (obj.GetType() != typeof (YearMonth)) return false;
            return Equals((YearMonth) obj);
        }

        public override int GetHashCode()
        {
            return ticks;
        }

        public int CompareTo(YearMonth other)
        {
            return ticks.CompareTo(other.ticks);
        }

        #endregion

        #region Discrete interface
        public YearMonth get_last()
        {
            if (Equals(FarPast))
                return FarPast;

            if (Equals(FarFuture))
                return FarFuture;
            return new YearMonth(ticks - 1);
        }
        public YearMonth get_last(int Dvalue)
        {
            if (Equals(FarPast))
                return FarPast;

            if (Equals(FarFuture))
                return FarFuture;
            return new YearMonth(ticks - Dvalue);
        }

        public YearMonth get_next()
        {
            if (Equals(FarPast))
                return FarPast;

            if (Equals(FarFuture))
                return FarFuture;
            return new YearMonth(ticks + 1);
        }

        public YearMonth get_next(int DValue)
        {
            if (Equals(FarPast))
                return FarPast;

            if (Equals(FarFuture))
                return FarFuture;
            return new YearMonth(ticks + DValue);
        }
        #endregion 

         public static implicit operator DateTime(YearMonth year_month)
         {
             return year_month.as_date_Time();
         }

        public static implicit operator YearMonth(DateTime date_time)
        {
            return new YearMonth(date_time);
        }
    }
}

（本文版權(quán)屬于? 2012 - 2013 予沁安 | 轉(zhuǎn)載請(qǐng)注明作者和出處）