CODEWITHSUNDEEP
c#t-sqldatetime
jaffa
jaffa

Reputation: 27350

How can I emulate TSQL's DateDiff correctly in C#

I seem to get different results when using the TimeSpan functionality in C# against TSQL DateDiff. It seems that DateDiff gives the number of days between 2 dates regardless of the time-stamp, whereas in C# it takes into consideration the timestamp. So if the 1st timestamp is at 10am, and the 2nd timestamp is at 9am the following day, the timespan is 0 days, whereas DateDiff will return 1.

declare @d1 datetime
declare @d2 datetime

set @d1 = '2/9/2011 10:00'
set @d2 = '2/10/2011 09:00'

select datediff(day, @d1, @d2)
-- prints 1

Using C# DateTime and DateTime span.

  // will return 1 with same dates
  private static int DateDiff(DateTime from, DateTime to)
  {
        return (new DateTime(from.Year, from.Month, from.Day)
                - new DateTime(to.Year, to.Month, to.Day)).Days;            
  }

Question is, is there a better way to do this?

Upvotes: 2

Views: 1640

Answers (3)

Arion
Arion

Reputation: 31239

Something like this:

private static int DateDiff(DateTime From, DateTime To)
{
    return From.Subtract(To).Days;            
}

Upvotes: 0

FiveTools
FiveTools

Reputation: 6030

 public enum DateInterval
    {
        Second, Minute, Hour, Day, Week, Month, Quarter, Year
    }

  public long DateDiff(DateInterval Interval, System.DateTime StartDate, System.DateTime EndDate)
    {
        long lngDateDiffValue = 0;
        System.TimeSpan TS = new System.TimeSpan(EndDate.Ticks - StartDate.Ticks);
        switch (Interval)
        {
            case DateInterval.Day:
                lngDateDiffValue = (long)TS.Days;
                break;
            case DateInterval.Hour:
                lngDateDiffValue = (long)TS.TotalHours;
                break;
            case DateInterval.Minute:
                lngDateDiffValue = (long)TS.TotalMinutes;
                break;
            case DateInterval.Month:
                lngDateDiffValue = (long)(TS.Days / 30);
                break;
            case DateInterval.Quarter:
                lngDateDiffValue = (long)((TS.Days / 30) / 3);
                break;
            case DateInterval.Second:
                lngDateDiffValue = (long)TS.TotalSeconds;
                break;
            case DateInterval.Week:
                lngDateDiffValue = (long)(TS.Days / 7);
                break;
            case DateInterval.Year:
                lngDateDiffValue = (long)(TS.Days / 365);
                break;
        }
        return (lngDateDiffValue);
    }//end of DateDiff

I found this method works for me.

Upvotes: 0

Klaus Byskov Pedersen
Klaus Byskov Pedersen

Reputation: 120937

You could make your method shorter, like this:

private static int DateDiff(DateTime from, DateTime to)
{
    return (to.Date - from.Date).Days;            
}

Upvotes: 3

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