c# 公元转农历

void Main()
{
    var date = new DateTime(2017,7,30);
    GetLunarDisplay(date).Dump();
}

public List<string> GetLunarYearList()
{
    var q1 = "甲乙丙丁戊己庚辛壬癸";
    var q2 = "子丑寅卯辰巳午未申酉戌亥";
    var yearList = new List<string>();
    var index1 = 0;
    var index2 = 0;
    while (!(index1 == 0 && index2 == 0 && yearList.Count > 0))
    {
        yearList.Add(q1[index1] + "" + q2[index2] + "年");
        index1 = (index1 + 1) % 10;
        index2 = (index2 + 1) % 12;
    }

    return yearList;
}

public List<string> GetLunarMonthList()
{
    var monthList = new List<string> { "正月", "二月", "三月", "四月", "五月", "六月", "七月", "八月", "九月", "十月", "十一月", "腊月" };
    return monthList;
}

public List<string> GetLunarDayList()
{
    var dayList = new List<string> 
        { "初一","初二","初三","初四","初五","初六","初七","初八","初九","初十"
        ,"十一","十二","十三","十四","十五","十六","十七","十八","十九"
        ,"廿一","廿二","廿三","廿四","廿五","廿六","廿七","廿八","廿九","三十"};
    return dayList;
}

public string GetLunarDisplay(DateTime date)
{
    var calendar = new System.Globalization.ChineseLunisolarCalendar();

    //获取农历的年月日
    var lunarYear = calendar.GetYear(date);
    var lunarMonth = calendar.GetMonth(date);
    var lunarDay = calendar.GetDayOfMonth(date);

    //获取农历年，公元前2679年为第一个甲子年
    var firstYear = -2697;
    var yearIndex = (lunarYear - firstYear - 1) % 60;   //公元纪年没有公元0年，是从1开始的，所以数学规则上要减一年
    var yearDisplay = GetLunarYearList()[yearIndex];

    //获取农历月
    int leapMonth = calendar.GetLeapMonth(lunarYear);
    var monthDisplay = GetLunarMonthList()[lunarMonth - 1];
    if (lunarMonth == leapMonth)
        monthDisplay = "闰" + GetLunarMonthList()[lunarMonth - 1 - 1];     //闰月月份减一
    else if (leapMonth > 0 && lunarMonth > leapMonth)
        monthDisplay = GetLunarMonthList()[lunarMonth - 1 - 1];            //闰月之后每个月份都要减一

    //获取农历日
    var dayDisplay = GetLunarDayList()[lunarDay - 1];

    //组件返回农历日期
    return yearDisplay + monthDisplay + dayDisplay;
}