How to access last element value in query syntax?

Question

Suppose I have this class:-

 

public class Availability
    {
        public DateTime StartDate { get; set; }
        public DateTime EndDate { get; set; }
    }

 

And a collection based on it:-

 

List<Availability> availability = new List<Availability>
{
      new Availability { StartDate = new DateTime(2015,1,5), EndDate = new DateTime(2015,1,10)},
      new Availability { StartDate = new DateTime(2015,1,15), EndDate = new DateTime(2015,1,20)},
      new Availability { StartDate = new DateTime(2015,1,22), EndDate = new DateTime(2015,1,28)}
};

 

Now, I am trying to write some query,(that query is very big

but I need help for particulat scenario)

 

var result = //Other query
             from a in availability
             where d < a.StartDate && d > ??

 

At "??" I want to access EndDate of last accessed list i.e. when query

is running for first object (05/Jan, 10/Jan) since it is first object

in collection I don't have any filter but when query is executing

second object i.e (15/Jan, 20/Jan) I want to access 10/Jan (EndDate

of last accessed object. But, `a` will currently hold the object with

date (15/Jan, 20/Jan) How to access previous one? I hope I am clear.