CODE EXAMPLE FOR CSHARP

LINQ: 2 join with group by

var query = (
        //Customers
        from customer in context.Customers

        //Engineer 1
        join engineer1 in context.Employees on customer.PrimaryEngineer equals
        engineer1.EmployeeId into eng1 
        from engineer1 in eng1.DefaultIfEmpty()

        //Engineer Top
        join engineerTop in context.Employees on customer.TopEngineer equals 
        engineerTop.EmployeeId into top
        from engineerTop in top.DefaultIfEmpty()
        group new {customer, engineer1, engineerTop} by new {CustName = customer.Name, EmpId1 = engineer1.EmployeeId, EmpId2 = engineerTop.EmployeeId} into grp
        select new
        {
            Name = grp.Key.CustName,
            EmpId1 = grp.Key.EmpId1,
            EmpId2 = grp.Key.EmpId2
        });