C# 获取上周和上月开始及结束时间

//获取上周开始时间（备注国内从周一至周日;国外从周日至周六）

public static DateTime getPreWeekStartTime()
{
var weekday = (int)DateTime.Now.DayOfWeek;
return Convert.ToDateTime(DateTime.Now.AddDays(-7 - weekday + 1).ToString("yyyy-MM-dd 00:00:00"));
}
//获取上周结束时间
public static DateTime getPreWeekEndTime()
{
int weekday = (int)DateTime.Now.DayOfWeek;
return Convert.ToDateTime(DateTime.Now.AddDays(weekday - 7 + 1).ToString("yyyy-MM-dd 23:59:59"));
}
//获取上月开始时间
public static DateTime getPreMonthStartTime()
{
return Convert.ToDateTime(DateTime.Now.AddMonths(-1).AddDays(1 - DateTime.Now.Day).ToString("yyyy-MM-dd 00:00:00"));
}
//获取上月结束时间
public static DateTime getPreMonthEndTime()
{
return Convert.ToDateTime(DateTime.Now.AddDays(-DateTime.Now.Day).ToString("yyyy-MM-dd 23:59:59"));
}