public static void GetEmployeesByDepartment()
{
var employeesByDepartment = Department.GetAllDepartments()
.GroupJoin(EmployeeWithDepartment.GetAllEmployees(),
d => d.ID,
e => e.DepartmentID,
(department, employees) => new
{
Department = department,
Employees = employees
});
var employeesByDepartment2 = from d in Department.GetAllDepartments()
join e in EmployeeWithDepartment.GetAllEmployees()
on d.ID equals e.DepartmentID into eGroup
select new
{
Department = d,
Employees = eGroup
};
foreach (var department in employeesByDepartment)
{
Console.WriteLine(department.Department.Name);
foreach (var employee in department.Employees)
{
Console.WriteLine(" " + employee.Name);
}
Console.WriteLine();
}
}
public static void GetEmployeesByDepartment()
{
var result = from e in EmployeeWithDepartment.GetAllEmployees()
join d in Department.GetAllDepartments()
on e.DepartmentID equals d.ID into eGroup
from d in eGroup.DefaultIfEmpty()
select new
{
EmployeeName = e.Name,
DepartmentName = d == null ? "No Department" : d.Name
};
///Rewrite Example 1 using extension method syntax.
///To implement Left Outer Join, with extension method syntax we use the GroupJoin() method along with SelectMany() and DefaultIfEmpty() methods.
var result2 = EmployeeWithDepartment.GetAllEmployees()
.GroupJoin(Department.GetAllDepartments(),
e => e.DepartmentID,
d => d.ID,
(emp, depts) => new { emp, depts })
.SelectMany(z => z.depts.DefaultIfEmpty(),
(a, b) => new
{
EmployeeName = a.emp.Name,
DepartmentName = b == null ? "No Department" : b.Name
});
foreach (var v in result)
{
Console.WriteLine(v.EmployeeName + "\t" + v.DepartmentName);
}
}
public static void GetEmployeesByDepartment()
{
var result = EmployeeWithDepartment.GetAllEmployees().Join(Department.GetAllDepartments(),
e => e.DepartmentID,
d => d.ID, (employee, department) => new
{
EmployeeName = employee.Name,
DepartmentName = department.Name
});
///Rewrite Example 1 using SQL like syntax.
///Notice that we are using the join operator but without into
var result2 = from e in EmployeeWithDepartment.GetAllEmployees()
join d in Department.GetAllDepartments()
on e.DepartmentID equals d.ID
select new
{
EmployeeName = e.Name,
DepartmentName = d.Name
};
///Notice that, in the output we don't have Andy record.
///This is because, Andy does not have a matching department in Department collection.
foreach (var employee in result)
{
Console.WriteLine(employee.EmployeeName + "\t" + employee.DepartmentName);
}
}
public static void GetEmployeesByDepartment()
{
var result = from e in EmployeeWithDepartment.GetAllEmployees()
from d in Department.GetAllDepartments()
select new { e, d };
///Rewrite Example 1 using extension method syntax
///To implement Cross Join using extension method syntax, we could either use SelectMany() method or Join() method
var result1_extend = Employee.GetAllEmployees()
.SelectMany(e => Department.GetAllDepartments(), (e, d) => new { e, d });
///Implementing cross join using Join()
var result1_extend2 = Employee.GetAllEmployees()
.Join(Department.GetAllDepartments(),
e => true,
d => true,
(e, d) => new { e, d });
foreach (var v in result)
{
Console.WriteLine(v.e.Name + "\t" + v.d.Name);
}
///In this case, every element from the Departments collection is combined with every element in the Employees collection.
var result2 = from d in Department.GetAllDepartments()
from e in Employee.GetAllEmployees()
select new { e, d };
foreach (var v in result2)
{
Console.WriteLine(v.e.Name + "\t" + v.d.Name);
}
}
