如何将时间四舍五入到最接近的X分钟？

DateTime RoundUp(DateTime dt, TimeSpan d){    return new DateTime((dt.Ticks + d.Ticks - 1) / d.Ticks * d.Ticks, dt.Kind);}

例：

var dt1 = RoundUp(DateTime.Parse("2011-08-11 16:59"), TimeSpan.FromMinutes(15));// dt1 == {11/08/2011 17:00:00}var dt2 = RoundUp(DateTime.Parse("2011-08-11 17:00"), TimeSpan.FromMinutes(15));// dt2 == {11/08/2011 17:00:00}var dt3 = RoundUp(DateTime.Parse("2011-08-11 17:01"), TimeSpan.FromMinutes(15));// dt3 == {11/08/2011 17:15:00}