How to truncate milliseconds off of a .NET DateTime
I'm trying to compare a time stamp from an incoming request to a database stored value. SQL Server of course keeps some precision of milliseconds on the time, and when read into a .NET DateTime, it includes those milliseconds. The incoming request to the system, however, does not offer that precision, so I need to simply drop the milliseconds.
I feel like I'm missing something obvious, but I haven't found an elegant way to do it (C#).
The following will work for a DateTime that has fractional milliseconds, and also preserves the Kind property (Local, Utc or Undefined).
DateTime dateTime = ... anything ...
dateTime = new DateTime(
dateTime.Ticks - (dateTime.Ticks % TimeSpan.TicksPerSecond),
dateTime.Kind
);
or the equivalent and shorter:
dateTime = dateTime.AddTicks( - (dateTime.Ticks % TimeSpan.TicksPerSecond));
This could be generalized into an extension method:
public static DateTime Truncate(this DateTime dateTime, TimeSpan timeSpan)
{
if (timeSpan == TimeSpan.Zero) return dateTime; // Or could throw an ArgumentException
return dateTime.AddTicks(-(dateTime.Ticks % timeSpan.Ticks));
}
which is used as follows:
dateTime = dateTime.Truncate(TimeSpan.FromMilliseconds(1)); // Truncate to whole ms
dateTime = dateTime.Truncate(TimeSpan.FromSeconds(1)); // Truncate to whole second
dateTime = dateTime.Truncate(TimeSpan.FromMinutes(1)); // Truncate to whole minute
...
var date = DateTime.Now;
date = new DateTime(date.Year, date.Month, date.Day, date.Hour, date.Minute, date.Second, date.Kind);
Here is an extension method based on a previous answer that will let you truncate to any resolution...
Usage:
DateTime myDateSansMilliseconds = myDate.Truncate(TimeSpan.TicksPerSecond);
DateTime myDateSansSeconds = myDate.Truncate(TimeSpan.TicksPerMinute)
Class:
public static class DateTimeUtils
{
/// <summary>
/// <para>Truncates a DateTime to a specified resolution.</para>
/// <para>A convenient source for resolution is TimeSpan.TicksPerXXXX constants.</para>
/// </summary>
/// <param name="date">The DateTime object to truncate</param>
/// <param name="resolution">e.g. to round to nearest second, TimeSpan.TicksPerSecond</param>
/// <returns>Truncated DateTime</returns>
public static DateTime Truncate(this DateTime date, long resolution)
{
return new DateTime(date.Ticks - (date.Ticks % resolution), date.Kind);
}
}