Ignore milliseconds when comparing two datetimes

Question

This is probably a dumb question, but I cannot seem to figure it out. I am comparing the LastWriteTime of two files, however it is always failing because the file I download

Answer 1

The most straightforward way to truncate time is to format it and parse on the units that you want:

var myDate = DateTime.Parse(DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss"));

DOK's method re-written

public bool CompareByModifiedDate(string strOrigFile, string strDownloadedFile)
    {
         DateTime dtOrig = DateTime.Parse(File.GetLastWriteTime(strOrigFile).ToString("MM/dd/yyyy hh:mm:ss"));
         DateTime dtNew = DateTime.Parse(File.GetLastWriteTime(strDownloadedFile).ToString("MM/dd/yyyy hh:mm:ss"));

         if (dtOrig == dtNew)
            return true;
         else
            return false;
    }

Answer 2

Don't know why almost all programmers needs extra lines to return a bool value from a function with a bool expression.

instead

if (dtOrig.ZeroMilliseconds() == dtNew.ZeroMilliseconds())
    return true;
 else
    return false;

you can always just use

return dtOrig.ZeroMilliseconds() == dtNew.ZeroMilliseconds()

if the expression is true it returns true else false.

Answer 3

You can subtract them, to get a TimeSpan.

Then use TimeSpan.totalSeconds()

Answer 4

You could create an extension method that would set the milliseconds to zero for a DateTime object

public static DateTime ZeroMilliseconds(this DateTime value) {
  return new DateTime(value.Year, value.Month, value.Day, 
    value.Hours, value.Minutes, value.Seconds);
}

Then in your function

 if (dtOrig.ZeroMilliseconds() == dtNew.ZeroMilliseconds())
        return true;
     else
        return false;

Answer 5

One way would be to create new dates, inputting the year, month, day, hour, minute, second into the constructor. Alternatively, you could simply compare each value separately.

Answer 6

I recommend you use an extension method:

public static DateTime TrimMilliseconds(this DateTime dt)
{
    return new DateTime(dt.Year, dt.Month, dt.Day, dt.Hour, dt.Minute, dt.Second, 0, dt.Kind);
}

then its just:

if (dtOrig.TrimMilliseconds() == dtNew.TrimMilliseconds())