C# 昨天今天明天上周本周下周上月本月下月等日期计算

//定义变量

private static DateTime currentDateTime; //当前时间
private static DateTime lastDateTime; //昨天时间
private static DateTime nextDateTime; //明天时间

private static int currentDayOfWeek; //今天星期几
private static int lastDayOfWeek; //昨天星期几
private static int nextDayOfWeek; //明天星期几

private static DateTime currentStartWeek; //本周周一
private static DateTime currentEndWeek; //本周周日
private static DateTime currentStartMonth; //本月月初
private static DateTime currentEndMonth; //本月月末
private static DateTime currentStartQuarter; //本季度初
private static DateTime currentEndQuarter; //本季度末
private static DateTime currentStartYear; //今年年初
private static DateTime currentEndYear; //今年年末

private static DateTime lastStartWeek; //上周周一
private static DateTime lastEndWeek; //上周周日
private static DateTime lastStartMonth; //上月月初
private static DateTime lastEndMonth; //上月月末
private static DateTime lastStartQuarter; //上季度初
private static DateTime lastEndQuarter; //上季度末
private static DateTime lastStartYear; //去年年初
private static DateTime lastEndYear; //去年年末

private static DateTime nextStartWeek; //下周周一
private static DateTime nextEndWeek; //下周周日
private static DateTime nextStartMonth; //下月月初
private static DateTime nextEndMonth; //下月月末
private static DateTime nextStartQuarter; //下季度初
private static DateTime nextEndQuarter; //下季度末
private static DateTime nextStartYear; //明年年初
private static DateTime nextEndYear; //明年年末

//计算变量

currentDateTime = DateTime.Now; //当前时间
lastDateTime = DateTime.Now.AddDays(-1); //昨天时间
nextDateTime = DateTime.Now.AddDays(1); //明天时间

currentDayOfWeek = Convert.ToInt32(currentDateTime.DayOfWeek.ToString("d")); //今天星期几
currentDayOfWeek = Convert.ToInt32(lastDateTime.DayOfWeek.ToString("d")); //昨天星期几
currentDayOfWeek = Convert.ToInt32(nextDateTime.DayOfWeek.ToString("d")); //明天星期几

currentStartWeek = currentDateTime.AddDays(1 - ((currentDayOfWeek == 0) ? 7 : currentDayOfWeek)); //本周周一
currentEndWeek = currentStartWeek.AddDays(6); //本周周日
lastStartWeek = currentStartWeek.AddDays(-7); //上周周一
lastEndWeek = currentEndWeek.AddDays(-7); //上周周日
nextStartWeek = currentStartWeek.AddDays(7); //下周周一
nextEndWeek = currentEndWeek.AddDays(7); //下周周日

currentStartMonth = currentDateTime.AddDays(1 - currentDateTime.Day); //本月月初
currentEndMonth = currentStartMonth.AddMonths(1).AddDays(-1); //本月月末
lastStartMonth = currentStartMonth.AddMonths(-1); //上月月初
lastEndMonth = currentStartMonth.AddDays(-1); //上月月末
nextStartMonth = currentEndMonth.AddDays(1); //下月月初
nextEndMonth = nextStartMonth.AddMonths(1).AddDays(-1); //下月月末

currentStartQuarter = currentDateTime.AddMonths(0 - (currentDateTime.Month - 1) % 3).AddDays(1 - currentDateTime.Day); //本季度初
currentEndQuarter = currentStartQuarter.AddMonths(3).AddDays(-1); //本季度末
lastStartQuarter = currentStartQuarter.AddMonths(-3); //上季度初
lastEndQuarter = currentStartQuarter.AddDays(-1); //上季度末
nextStartQuarter = currentEndQuarter.AddDays(1); //下季度初
nextEndQuarter = nextStartQuarter.AddMonths(3).AddDays(-1); //下季度末

//年度运算
currentStartYear = new DateTime(currentDateTime.Year, 1, 1); //今年年初
currentEndYear = new DateTime(currentDateTime.Year, 12, 31); //今年年末
lastStartYear = currentStartYear.AddYears(-1); //去年年初
lastEndYear = currentEndYear.AddYears(-1); //去年年末
nextStartYear = currentStartYear.AddYears(1); //明年年初
nextEndYear = currentEndYear.AddYears(1); //明年年末

/// <summary>
/// 返回星期几字符串函数
/// </summary>
/// <param name="myDateTime"></param>
/// <returns></returns>

private string GetWeekDayName(DateTime myDateTime)
{
string week = "";
//获取当前日期是星期几
string dt = myDateTime.DayOfWeek.ToString();
//根据取得的星期英文单词返回汉字
switch (dt)
{
case "Monday":
week = "星期一";
break;
case "Tuesday":
week = "星期二";
break;
case "Wednesday":
week = "星期三";
break;
case "Thursday":
week = "星期四";
break;
case "Friday":
week = "星期五";
break;
case "Saturday":
week = "星期六";
break;
case "Sunday":
week = "星期日";
break;
}
return week;
}