Question

Afternoon,

I would like to know how i would do this query in LINQ, can anyone please provide a hand.

 SELECT   Id, ExportDate,
         (SELECT        TOP (1) Id
          FROM            Orders
          WHERE        (PickupListId = PickingLists.Id)) AS StartOrderId,
         (SELECT        TOP (1) Id
          FROM            Orders AS Orders_1
          WHERE        (PickupListId = PickingLists.Id)
          ORDER BY Id DESC) AS EndOrderId,
         (SELECT        COUNT(Id) AS Expr1
          FROM            Orders AS Orders_2
          WHERE        (PickupListId = PickingLists.Id)) AS NumberOfOrders
 FROM     PickingLists
 ORDER BY ExportDate DESC

Update
I have updated my code as per Andrei’s solution, however there is an issue converting the ID’s please can you see what it could be?

 [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public List<GetPickingLists> GetPickingLists()
    {
        using (aboDataDataContext dc = new aboDataDataContext())
        {
            var query = from list in dc.pickingLists
                        orderby list.ExportDate descending
                        select new GetPickingLists
                        {
                            plId = list.Id,
                            plDate = list.ExportDate,
                            orderStart = Convert.ToInt32(dc.amzOrders.Where(order => order.pickupListId == list.Id).FirstOrDefault()),
                            orderEnd = Convert.ToInt32(dc.amzOrders.Where(order => order.pickupListId == list.Id).OrderByDescending(order => order.id).FirstOrDefault()),
                            orderCount = dc.amzOrders.Where(order => order.pickupListId == list.Id).Count(),
                        };

            return query.ToList();
        }
    }

I have created this to set up the response, not sure if this is needed. Cheers.

 public class GetPickingLists
{
    public int plId { get; set; }
    public int orderStart { get; set; }
    public int orderEnd { get; set; }
    public int orderCount { get; set; }
    public DateTime plDate { get; set; }
}

Answer 1

var query = from list in dbContext.PickingLists
            orderby list.ExportDate descending
            select new
            {
                list.Id,
                list.ExportDate,
                StartOrderId = dbContext.Orders.Where(order => order.PickupListId == list.Id).FirstOrDefault().Id,
                EndOrderId = dbContext.Orders.Where(order => order.PickupListId == list.Id).OrderByDescending(order => order.Id).FirstOrDefault().Id,
                NumberOfOrders = dbContext.Orders.Where(order => order.PickupListId == list.Id).Count(),
            }