C#判断两个日期是否在同一周，某日期是本月的第几周

/// <summary>
/// 判断两个日期是否在同一周
/// </summary>
/// <param name="dtmS">开始日期</param>
/// <param name="dtmE">结束日期</param>
/// <returns></returns>
private bool IsInSameWeek(DateTime dtmS, DateTime dtmE)
{
TimeSpan ts = dtmE - dtmS;
double dbl = ts.TotalDays;
int intDow = Convert.ToInt32(dtmE.DayOfWeek);
if (intDow == 0) intDow = 7;
if (dbl >= 7 || dbl >= intDow) return false;
else return true;
}

/// <summary>
/// 某日期是本月的第几周
/// </summary>
/// <param name="dtSel"></param>
/// <param name="sundayStart"></param>
/// <returns></returns>
private int WeekOfMonth(DateTime dtSel, bool sundayStart)
{
//如果要判断的日期为1号，则肯定是第一周了
if (dtSel.Day == 1) return 1;
else
{
//得到本月第一天
DateTime dtStart = new DateTime(dtSel.Year, dtSel.Month, 1);
//得到本月第一天是周几
int dayofweek = (int)dtStart.DayOfWeek;
//如果不是以周日开始，需要重新计算一下dayofweek，详细风DayOfWeek枚举的定义
if (!sundayStart)
{
dayofweek = dayofweek - 1;
if (dayofweek < 0) dayofweek = 7;
}
//得到本月的第一周一共有几天
int startWeekDays = 7 - dayofweek;
//如果要判断的日期在第一周范围内，返回1
if (dtSel.Day <= startWeekDays) return 1;
else
{
int aday = dtSel.Day + 7 - startWeekDays;
return aday / 7 + (aday % 7 > 0 ? 1 : 0);
}
}
}