Check if a date range is within a date range

Asked 2010-09-24T12:00:34.120

I have the following class:

public class Membership
{
    public DateTime StartDate { get; set; }
    public DateTime? EndDate { get; set; } // If null then it lasts forever
}

I need to make sure when adding to the following list that the new item doesn't overlap the dates from existing item:

var membership = new List<Membership>
{
    new Membership { StartDate = DateTime.UtcNow.AddDays(-10), EndDate = DateTime.UtcNow.AddDays(-5) },
    new Membership { StartDate = DateTime.UtcNow.AddDays(-5), EndDate = null }
};

For example doing:

var newItem = new Membership { StartDate = DateTime.UtcNow.AddDays(-15), EndDate = DateTime.UtcNow.AddDays(-10) }; // Allowed

var newItem2 = new Membership { StartDate = DateTime.UtcNow.AddDays(-15), EndDate = null }; // Not Allowed

if (AllowededToAdd(newItem))
    membership.Add(newItem);

if (AllowededToAdd(newItem2))
    membership.Add(newItem2);

I thought this would be simple but so far my attempts have all been wrong and i'm starting to confuse myself and was hoping someone had done something similar they could share. Thanks

Edit Report

2 Answers

Basically, a date range overlaps another if any of its endings are within the other range, or vice versa.

static bool AllowedToAdd(List<Membership> membershipList, Membership newItem)
{
    return !membershipList.Any(m =>
        (m.StartDate < newItem.StartDate &&
         newItem.StartDate < (m.EndDate ?? DateTime.MaxValue))
        ||
        (m.StartDate < (newItem.EndDate ?? DateTime.MaxValue) &&
         (newItem.EndDate ?? DateTime.MaxValue) <= (m.EndDate ?? DateTime.MaxValue))
        ||
        (newItem.StartDate < m.StartDate &&
         m.StartDate < (newItem.EndDate ?? DateTime.MaxValue))
        ||
        (newItem.StartDate < (m.EndDate ?? DateTime.MaxValue) &&
         (m.EndDate ?? DateTime.MaxValue) <= (newItem.EndDate ?? DateTime.MaxValue))
        );
}

With the usage:

if (AllowedToAdd(membershipList, newItem))
    membershipList.Add(newItem);

answered 2010-09-24T12:11:20.913

public bool DoesAnOfferAlreadyExistWithinTheTimeframeProvided(int RetailerId, DateTime ValidFrom, DateTime ValidTo)
        {
            bool result = true;

            try
            {
                // Obtain the current list of coupons associated to the retailer.
                List<RetailerCoupon> retailerCoupons = PayPalInStore.Data.RetailerCoupon.Find(x => x.RetailerId == RetailerId).ToList();

                // Loop through each coupon and see if the timeframe provided in the NEW coupon doesnt fall between any EZISTING coupon.
                if (retailerCoupons != null)
                {
                    foreach (RetailerCoupon coupon in retailerCoupons)
                    {
                        DateTime retailerCouponValidFrom = coupon.DateValidFrom;
                        DateTime retailerCouponValidTo = coupon.DateExpires;

                        if ((ValidFrom <= retailerCouponValidFrom && ValidTo <= retailerCouponValidFrom) || (ValidFrom >= retailerCouponValidTo && ValidTo >= retailerCouponValidTo))
                        {
                            return false;
                        }
                    }
                }

                return result;
            }
        catch (Exception ex)
        {
            this.errorManager.LogError("DoesAnOfferAlreadyExistWithinTheTimeframeProvided failed", ex);
            return result;
        }
    }

answered 2012-04-23T13:38:15.493

Check if a date range is within a date range

2 Answers

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