How to loop between two dates

Question

I have a calendar which passes selected dates as strings into a method. Inside this method, I want to generate a list of all the dates starting from the selected start date and

Answer 1

An alternative method

public static class MyExtensions
{
    public static IEnumerable EachDay(this DateTime start, DateTime end)
    {
        // Remove time info from start date (we only care about day). 
        DateTime currentDay = new DateTime(start.Year, start.Month, start.Day);
        while (currentDay <= end)
        {
            yield return currentDay;
            currentDay = currentDay.AddDays(1);
        }
    }
}

Now in the calling code you can do the following:

DateTime start = DateTime.Now;
DateTime end = start.AddDays(20);
foreach (var day in start.EachDay(end))
{
    ...
}

Another advantage to this approach is that it makes it trivial to add EachWeek, EachMonth etc. These will then all be accessible on DateTime.

Answer 2

The easiest thing to do would be take the start date, and add 1 day to it (using AddDays) until you reach the end date. Something like this:

DateTime calcDate = start.Date;
while (calcDate <= end)
{
    calcDate = calcDate.AddDays(1);
    calculatedDates.Add(calcDate.ToString());
}

Obviously, you would adjust the while conditional and the position of the AddDays call depending on if you wanted to include the start and end dates in the collection or not.

[Edit: By the way, you should consider using TryParse() instead of Parse() in case the passed in strings don't convert to dates nicely]

Answer 3

for( DateTime i = start; i <= end; i = i.AddDays( 1 ) )
{
    Console.WriteLine(i.ToShortDateString());
}

Answer 4

You just need to iterate from start to end, you can do this in a for loop

DateTime start = DateTime.Parse(startDate);
DateTime end = DateTime.Parse(endDate);

for(DateTime counter = start; counter <= end; counter = counter.AddDays(1))
{
    calculatedDates.Add(counter);
}

Answer 5

static IEnumerable<DateTime> AllDatesBetween(DateTime start, DateTime end)
{
    for(var day = start.Date; day <= end; day = day.AddDays(1))
        yield return day;
}

Edit: Added code to solve your particular example and to demonstrate usage:

var calculatedDates = 
    new List<string>
    (
        AllDatesBetween
        (
            DateTime.Parse("2009-07-27"),
            DateTime.Parse("2009-07-29")
        ).Select(d => d.ToString("yyyy-MM-dd"))
    );