Question

While trying a sem-complex query to display some ListView content on the page I got stuck on the famous “Only parameterless contstructor and initializers are supported in LINQ to Entities” error.

Here is the code I used … I can’t find a place where I initialized something inside the query with parameters ….

protected void ArtistsList()
{
    Guid cat1 = new Guid("916ec8ae-8336-43b1-87c0-8536b2676560");
    Guid cat2 = new Guid("92f2a07f-0570-4521-870a-bf898d1e92d6");

    var memberOrders = (from o in DataContext.OrderSet
                        where o.Status == 1 || o.Status == 0
                        select o.ID);

    var memberOrderDetails = (from o in DataContext.OrderDetailSet
                              where memberOrders.Any(f => f == o.Order.ID)
                              select o.Product.ID );

    var inventoryItems = (from i in DataContext.InventoryItemSet
                          select i.Inventory.Product.ID);

    var products = (from p in DataContext.ProductSet
                    join m in DataContext.ContactSet on p.ManufacturerID equals m.ID
                    where p.Active == true
                       && p.ShowOnWebSite == true
                       && p.Category.ID != cat1
                       && p.Category.ID != cat2
                       && p.AvailableDate <= DateTime.Today
                       && (p.DiscontinuationDate == null || p.DiscontinuationDate >= DateTime.Today)
                       && memberOrderDetails.Any(f => f != p.ID)
                       && inventoryItems.Any(f => f == p.ID)
                    select new { ContactID = m.ID, ContactName = m.Name });

    artistsRepeater.DataSource = products;
    artistsRepeater.DataBind();

    Response.Write("PRODUCT COUNT: " + products.Count());
}

The error itself pops on the line artistsRepeater.DataSource = products;

I tried to comment the lines && memberOrderDetails.Any(f => f != p.ID) and && inventoryItems.Any(f => f == p.ID) , still doesn’t change anything

Any hints ?

[edit]

With LINQpad, it works with the join but with it is bugging on the commented line

(from p in Products
join m in Members on p.ManufacturerID.Value equals m.ID
where p.Active == true
&& p.ShowOnWebSite == true
&& p.AvailableDate <= DateTime.Today
&& (p.DiscontinuationDate == null || p.DiscontinuationDate >= DateTime.Today)
//&& (from od in MemberOrderDetails where (from mo in MemberOrders where mo.Status == 1 || mo.Status == 0 select mo.ID).Any(f => f == od.ID) select od.Product.ID)
&& (from inv in InventoryItems select inv.Inventory.ProductID).Any(i => i.Value == p.ID)
select m).Distinct()

[edit-2]

It seems that this query in LINQpad is ok :

(from p in Products
join m in Members on p.ManufacturerID.Value equals m.ID
where p.Active == true
&& p.ShowOnWebSite == true
&& p.AvailableDate <= DateTime.Today
&& (p.DiscontinuationDate == null || p.DiscontinuationDate >= DateTime.Today)
&& !(from od in MemberOrderDetails where (from mo in MemberOrders where mo.Status == 1 || mo.Status == 0 select mo).Any(f => f.ID == od.ID) select od.Product.ID).Any(i => i == p.ID)
&& (from inv in InventoryItems select inv.Inventory.ProductID).Any(i => i.Value == p.ID) 
select m)

Answer 1

OK, this is subtle, but what if you change your LINQPad query from:

           (from p in Products
            join m in Members 
                on p.ManufacturerID.Value equals m.ID
            where p.Active == true
                && p.ShowOnWebSite == true
                && p.AvailableDate <= DateTime.Today
                && (p.DiscontinuationDate == null || p.DiscontinuationDate >= DateTime.Today)
                && (from od in MemberOrderDetails 
                    where (from mo in MemberOrders 
                           where mo.Status == 1 || mo.Status == 0 
                           select mo.ID).Any(f => f == od.ID) 
                    select od.Product.ID)
                && (from inv in InventoryItems 
                    select inv.Inventory.ProductID).Any(i => i.Value == p.ID)

…to:

           (from p in Products
            join m in Members 
                on p.ManufacturerID.Value equals m.ID
            where p.Active == true
                && p.ShowOnWebSite == true
                && p.AvailableDate <= DateTime.Today
                && (p.DiscontinuationDate == null || p.DiscontinuationDate >= DateTime.Today)
                && (from od in MemberOrderDetails 
                    where (from mo in MemberOrders 
                           where mo.Status == 1 || mo.Status == 0 
                           select mo).Any(f => f.ID == od.ID)          // NOTE!
                    select od.Product.ID)
                && (from inv in InventoryItems 
                    select inv.Inventory.ProductID).Any(i => i.Value == p.ID)

Why? I think type inference might be doing you wrong here. I’ve seen a similar thing with DateTimes.