从实体列表中查找实体

Question

I have a list of entities like below.

Entity1 { Id=1, From=01/01/2011, To=31/01/2011, Status=true }
Entity2 { Id=1, From=01/02/2011, To=28/02/2011, Status=false}
Entity2 { Id=2, From=01/02/2011, To=28/02/2011, Status=false}
Entity3 { Id=3, From=01/01/2011, To=31/01/2011, Status=true }
Entity4 { Id=4, From=01/01/2011, To=31/01/2011, Status=true }
Entity5 { Id=1, From=01/03/2011, To=31/03/2011, Status=false}
Entity6 { Id=4, From=31/03/2011, To=10/04/2011, Status=false}

I want to find the entities which have the oldest from date and latest last date. ( entities covering whole from date and to date)

Basically I need to get the entities which have distinct from and to dates. Also the starting entity should have the oldest From date and final entity should have the latest To date

In this case the expected result is entities starting from 01/01/2011 to 10/04/2011 .

Update

Entity 1 has the oldest from date : 01/01/2011
Entiry 2 which falls under : 01/01/2011 and 10/04/2011
Entity 3 which falls under 01/01/2011 and 10/04/2011(but entity 1 has same from and to date as Entity3 so entity 3 not a valid)
Entity 4 which falls under 01/01/2011 and 10/04/2011(but entity 1 has same from and to date as Entity4 so entity 4 not a valid)
Entity 5 which falls under : 01/01/2011 and 10/04/2011
Entity 6 has the most recent To date : 10/04/2011
So Valid entries are Entity1, Entity2, Entity5, Entity6

I tried something like this

var dates = (EntityList.GroupBy(offer => offer.id)
             .Select(group =>
                 new { offerid = group.Key,
                       offers = group.OrderBy(o => o.From)
                       })
             .OrderBy(g => g.offers.First().From) 
        . FirstOrDefault
 ().offers.First();  

But I think it should do without grouping, but I am not quite sure

Any help is appreciate

Thanks

Answer 1

var dates = from e in EntityList
            orderby e.Id
            group e by new { e.From, e.To } into g
            select g.First();

Query will return only first (ordered by id) entities from groups with same from-to dates.

Answer 2

Couldn't you use something like this:

var selectedEntity = EntityList.OrderBy(e => e.From)
                               .ThenByDescending(e => e.To)
                               .FirstOrDefault();

UPDATE:

Could you use the Distinct method?

var selectedEntity = EntityList.OrderBy(e => e.From)
                               .ThenByDescending(e => e.To)
                               .Distinct();