这是用TimeSpan代表几十年的最佳方式吗？

Question

I'm making a graph that cover "1930-1940", "1940-1950", "1950-1960", "1960-1970", ...

I want to represent this with a DateTime and a Timespan , but I'm not really sure how to make the TimeSpan , and I find it hard to verify if my timespans are correct.

Is this how I should use TimeSpan , or does it overlap? If it's overlapning then how can I fix it?

List<DateTime> list1 = new List<DateTime>();
List<TimeSpan> list2 = new List<TimeSpan>();

int startYearInt = 1930;

int times = 0;
const int intervalSize = 10;
for (int i = startYearInt; i < 2020; i += intervalSize)
{
    DateTime sYear = new DateTime(startYearInt + (intervalSize * times++), 1, 1);
    TimeSpan period = (sYear.AddYears(intervalSize)) - sYear;

    list1.Add(sYear);
    list2.Add(period); // <<-- Don't know if if this is correct?
}

EDIT: I have this too. And if My timespan is too small or to last it can give some problems.

public bool IsInsidePeriod(DateTime dt)
{
    return dt >= FromYearDateTime && dt < FromYearDateTime.Add(periodTimeSpan);
}

Answer 1

You're better off creating a DateRange value type than using a DateTime and a TimeSpan like that. Look here for an example. You can then have a factory method that gives you a range for a decade: DateRange.DecadeStartingOn(1930); . This way, you raise the level of abstraction and deal with the concepts you're referring to in the code itself .

Your IsInsidePeriod is a simple operation for the DateRange :

public bool Includes(DateTime date) {
  return start <= date && date <= end;
}

(assuming both start and end are inclusive )

Now, if you only need to deal with decades , you don't really need a full DateRange class, just this:

class Decade {

  public int StartYear { get; private set; }
  public int EndYear { get { return StartYear + 9; } }

  public Decade(int startYear) {
    StartYear = startYear;
  }

  public bool Includes(DateTime date) {
    return StartYear <= date.Year && date.Year <= EndYear;
  }

  public override string ToString() {
    return string.Format("{0}-{1}", StartYear, EndYear + 1);
  }

}

Or maybe a more general YearRange .

Answer 2

If all you are asking to do is solve your current issues then the code below works, hey I'm bored, I would however consider doing some research on DateTime ranges, comparisons (especially how the work with different TimeZones etc and intervals.

DateTime on MSDN

class Program
{   
    static void Main(string[] args)
    {
        int interval = 10;
        DateTime isInRangeDate = DateTime.UtcNow;

        for (int i = 1930; i < 2020; )
        {
            DateRange range = new DateRange(1, 1, i, interval);
            Console.WriteLine(string.Format("{0}: Is in range - {1}", range.ToString(), range.IsInsidePeriod(isInRangeDate)));


            i = range.EndDate.Year;
        }               

        Console.ReadLine();
    }  
}


public class DateRange
{
    public DateTime StartDate { get; private set; }
    public DateTime EndDate { get; private set; }

    public override string ToString()
    {
        return string.Format("{0}-{1}", this.StartDate.Year, this.EndDate.Year);
    }

    public DateRange(int day, int month, int year, int addYears)
    {
        StartDate = new DateTime(year, month, day, 0, 0, 0);
        EndDate = StartDate.AddYears(addYears);
    }

    public bool IsInsidePeriod(DateTime dt)
    {
        return ((dt.Date >= StartDate) && (dt.Date < EndDate));
    }
}

Answer 3

You can simplify your IsInPeriod method to something like this:

public bool IsInsidePeriod(DateTime dateToCompare, DateTime startDate, DateTime endDate)
{
    return startDate <= dateToCompare && dateToCompare < endDate;
}

As others have mentioned, TimeSpan is not buying you anything and is overcomplicating your described issue. Pay particular attention to the comparison operators. You may want either end to be exclusive rather than inclusive or vice versa.