Check if date range is sequential in c#?

问题

Assume I have a user interface where the user can select days. Is there a way to check if the days selected are sequential, such as:

4/4, 4/5, 4/6, 4/7, 4/8, 4/9, 4/10 or

4/29, 4/30, 5/1, 5/2, 5/3

I know I probably can loop through the date range and check, but I was more curious if there was a built in method already to check for this.

Regarding the above scenarios, they are in order and they can roll over into the next month.

I am using the .NET Framework 2.0 and can't use LINQ.

Regarding Tom's answer:

DateTime dtStart = new DateTime(2011,5,4);
DateTime dtEnd = new DateTime(2011,5,11);

int numberOfDaysSelected = 7; //Assume 7 days were selected.

TimeSpan ts = dtEnd - dtStart;


if(ts.Days == numberOfDaysSelected - 1)
{
Console.WriteLine("Sequential");
}
else
{
Console.WriteLine("Non-Sequential");
}

回答1:

I do not believe there is a built in method to achieve your desired results but if you can easily tell the earliest and latest dates, you could create a new TimeSpan by subtracting the the earliest date from the latest date and then verifying that the number of days of the timespan matches the number of dates selected - 1.

回答2:

You didn't tell us if the days are ordered.

You didn't tell us if they might fall over a month boundary as in

30, 31, 1.

I'll assume ordered, and I'll assume they won't fall over a month boundary (because your example is ordered, and it doesn't fall over a month boundary).

Then you can say

public bool IsSequential(this IEnumerable<DateTime> sequence) {
    Contract.Requires(sequence != null);
    var e = sequence.GetEnumerator();
    if(!e.MoveNext()) {
        // empty sequence is sequential
        return true;
    }
    int previous = e.Current.Date;
    while(e.MoveNext()) {
        if(e.Current.Date != previous.AddDays(1)) {
            return false;
        }      
        previous = e.Current.Date;
    }
    return true;
}

Note that this solution requires only walking the sequence once. If you don't have an ordered sequence, or if you permit falling over a month boundary the solution is more complicated.

回答3:

Nothing built in but you can build one easily using Linq:

List<DateTime> timeList = new List<DateTime>();
//populate list..
bool isSequential = timeList.Zip(timeList.Skip(1), 
                                 (a, b) => b.Date == a.Date.AddDays(1))
                            .All(x => x);

Edited - misunderstood question first to mean ascending in time as opposed to sequential - fixed that.

回答4:

Extension method using Linq:

public static bool IsContiguous(this IEnumerable<DateTime> dates)
{
    var startDate = dates.FirstOrDefault();

    if (startDate == null)
        return true;

    //.All() doesn't provide an indexed overload :(
    return dates
        .Select((d, i) => new { Date = d, Index = i })
        .All(d => (d.Date - startDate).Days == d.Index);
}

Testing it:

List<DateTime> contiguousDates = new List<DateTime>
{
    new DateTime(2011, 05, 05),
    new DateTime(2011, 05, 06),
    new DateTime(2011, 05, 07),
};
List<DateTime> randomDates = new List<DateTime>
{
    new DateTime(2011, 05, 05),
    new DateTime(2011, 05, 07),
    new DateTime(2011, 05, 08),
};

Console.WriteLine(contiguousDates.IsContiguous());
Console.WriteLine(randomDates.IsContiguous());

Returns

True
False

EDIT:

.NET 2-like answer:

public static bool CheckContiguousDates(DateTime[] dates)
{
    //assuming not null and count > 0
    var startDate = dates[0];

    for (int i = 0; i < dates.Length; i++)
    {
        if ((dates[i] - startDate).Days != i)
            return false;
    }
    return true;
}

回答5:

You can use the TimeGapCalculator of the Time Period Library for .NET to find gaps between multiple time periods (independent of order, count and overlapping):

// ----------------------------------------------------------------------
public void SequentialPeriodsDemo()
{
  // sequential
  ITimePeriodCollection periods = new TimePeriodCollection();
  periods.Add( new Days( new DateTime( 2011, 5, 4 ), 2 ) );
  periods.Add( new Days( new DateTime( 2011, 5, 6 ), 3 ) );
  Console.WriteLine( "Sequential: " + IsSequential( periods ) );

  periods.Add( new Days( new DateTime( 2011, 5, 10 ), 1 ) );
  Console.WriteLine( "Sequential: " + IsSequential( periods ) );
} // SequentialPeriodsDemo

// --------------------------------------------------------------------
public bool IsSequential( ITimePeriodCollection periods, ITimePeriod limits = null )
{
  return new TimeGapCalculator<TimeRange>( 
    new TimeCalendar() ).GetGaps( periods, limits ).Count == 0;
} // IsSequential

来源：https://stackoverflow.com/questions/5887079/check-if-date-range-is-sequential-in-c

标签

.net-2.0