Linq complex object groupBy

Question

I have fairly simple structure:
Each Customer has his WeeklyOrder .
WeeklyOrder consists of 5 DailyOrders and
in each DailyOrder are 5 OrderItems with ItemType (one of 5 slots basically) and Count .

I want to get counts for this week. So I get all DailyOrders from all users for this week.

var orders = db
    .WeeklyOrders
    .Where(x => x.WeekNumber == week && x.Year == year)
    .SelectMany(x => x.DailyOrders);

Everything works fine, but now i don't know how to group daily orders by DailyOrder.DayNumber and how to group items in each DailyOrder (not all together, for each daily order separately) so i know the sum from all users - how many items of type 1 were ordered for Monday how many for Tuesday etc.

I am asking only for the correct linq query.

To give you and idea of what I want to get in my view:

Monday

• Item1: x1
• Item2: y1
• Item3: z1
• Item4: u1
• Item5: v1

Tuesday

• Item1: x2
• Item2: y2
• Item3: z2
• Item4: u2
• Item5: v2

...
etc.

Here is my model:

public class WeeklyOrder
{
    public int WeeklyOrderId { get; set; }
    public int UserId { get; set; }
    public int Year { get; set; }
    public int WeekNumber { get; set; }

    public virtual Customer Customer { get; set; }
    public virtual List<DailyOrder> DailyOrders { get; set; }
}

public class DailyOrder
{
    public int DailyOrderId { get; set; }
    public int DayNumber { get; set; }
    public int WeeklyOrderId { get; set; }

    public virtual WeeklyOrder WeeklyOrder { get; set; }
    public virtual List<OrderItem> OrderItems { get; set; }
}

public class OrderItem
{
    public int OrderItemId { get; set; }
    public int Count { get; set; }
    public int ItemTypeId { get; set; }
    public int DailyOrderId { get; set; }

    public virtual DailyOrder DailyOrder { get; set; }
    public virtual ItemType Type { get; set; }
}

Answer 1

Try this:

var orders = db
    .WeeklyOrders
    .Where(x => x.WeekNumber == week && x.Year == year)
    .SelectMany(x => x.DailyOrders.SelectMany(y => y.OrderItems))
    .GroupBy(a => new
    {
        DayNumber = a.DailyOrder.DayNumber,
        Type = a.Type
    })
    .Select(a => new
    {
        DayNumber = a.Key.DayNumber,
        Type = a.Key.Type,
        Total = a.Sum(b => b.Count)
    });