using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Data.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var table = new List<Row>();

        table.Add(new Row{ID=1,Week=1,Value = 1000});

        table.Add(new Row{ID=2,Week=1,Value = 1000});

        table.Add(new Row{ID=3,Week=2,Value = 1000});

        table.Add(new Row{ID=4,Week=3,Value = 1000});

        table.Add(new Row{ID=5,Week=3,Value = 1000});

        table.Add(new Row{ID=6,Week=3,Value = 1000});

        var weeks = new List<int>{1,2,3,4};

​

        var q = from w in weeks

            join rw in (

            from r in table

            group r by r.Week into g

            select new {week = g.Key, count = g.Count()}) on w  equals rw.week into p

            from x2 in p.DefaultIfEmpty()

            select new {w, count = (x2 != null ? x2.count : 0)};

        var x = q.ToList();

        x.ForEach(i=>  Console.WriteLine(i));

    }

}

​

​

public class Row

{

    public int ID{get;set;}

    public int Week {get;set;}

    public int Value {get;set;}

}