Check if a date range is within a date range

Question

I have the following class:

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


        

Answer 1

Here's a solution (missing null argument-validation, and validation within Membership that EndDate > StartDate) using Collection:

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

    private DateTime NullSafeEndDate { get { return EndDate ?? DateTime.MaxValue; } }  

    private bool IsFullyAfter(Membership other)
    {
       return StartDate > other.NullSafeEndDate;
    }

    public bool Overlaps(Membership other)
    {
      return !IsFullyAfter(other) && !other.IsFullyAfter(this);
    }
}


public class MembershipCollection : Collection
{
   protected override void InsertItem(int index, Membership member)
   {
       if(CanAdd(member))
          base.InsertItem(index, member);
       else throw new ArgumentException("Ranges cannot overlap.");
   }

   public bool CanAdd(Membership member) 
   {
       return !this.Any(member.Overlaps);
   }
}