Group by results in ling

Question

I have linq statement that returns value. The LINQ statement below will returns the systemUser Id and totalHours of a systemUser as shown below. However, what I really what is to get the Id and the total hours per system user. How to add group then in linq?

var th1 = (from ss in db.SystemUsers
    join t in db.Timesheets on ss.Id equals t.SystemUser
    where (t.Project == projectId && t.StartTime >= year_start && t.StartTime < year_end)
    select new
    {
        ss.Id,
        t.TotalHours
    });

---

 Id     |   TotalHours
  1     |     10
  1     |     20
  2     |     10
  2     |     5 
 and so on...

---

EXPECTED OUTPUT

 Id     |   TotalHours
  1     |     30
  2     |     15
 and so on...

Answer 1

You have to use GroupBy

var th1 = 
    from ss in db.SystemUsers
    join t in db.Timesheets on ss.Id equals t.SystemUser
    where (t.Project == projectId && t.StartTime >= year_start && t.StartTime < year_end)
    group t by new { ss.Id } into g
    select new
    {
        g.Key.Id,
        TotalHours = g.Sum(x => x.TotalHours)
    };