Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/managers/implementations/EmployeeManager.vb
===================================================================
diff -u -r1712 -r1714
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/managers/implementations/EmployeeManager.vb	(.../EmployeeManager.vb)	(revision 1712)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/managers/implementations/EmployeeManager.vb	(.../EmployeeManager.vb)	(revision 1714)
@@ -2,20 +2,57 @@
     Implements IEmployeeManager
 
     Private ReadOnly _employees As ICollection(Of IEmployee)
+    ''' <inheritdoc/>
     Public ReadOnly Property Employees As ICollection(Of IEmployee) Implements IEmployeeManager.Employees
         Get
             Return New HashSet(Of IEmployee)(_employees)
         End Get
     End Property
 
+    ''' <inheritdoc/>
+    Public ReadOnly Property AvailableEmployees As ICollection(Of IEmployee) Implements IEmployeeManager.AvailableEmployees
+        Get
+            'Select the employees from the collection of all employees, which are not selected yet.
+            'The employees are compared on their initials in lowercase.
+            Return New HashSet(Of IEmployee)(_employees.Where(Function(employee) _
+                                                                 Not _selectedEmployees.Any(Function(selectedEmployee) _
+                                                                                               employee.Equals(selectedEmployee))))
+        End Get
+    End Property
+
+    Private ReadOnly _selectedEmployees As New List(Of IEmployee)
+    ''' <inheritdoc/>
+    Public ReadOnly Property SelectedEmployees As ICollection(Of IEmployee) Implements IEmployeeManager.SelectedEmployees
+        Get
+            Return New HashSet(Of IEmployee)(_selectedEmployees)
+        End Get
+    End Property
+
     Sub New()
         'Initial fetching of employees, then stored.
         _employees = EmployeesDatabaseMapper.FetchEmployees()
     End Sub
 
     ''' <inheritdoc/>
     Public Sub SelectEmployee(employee As IEmployee) Implements IEmployeeManager.SelectEmployee
-       
+        'Check whether or not that employee is already picked.
+        If _selectedEmployees.Any(Function(selectedEmployee) selectedEmployee.Equals(employee)) Then
+            'Employee was picked already.
+            Throw New Exception("Employee was already chosen.")
+        End If
+        'Add employee to list of selected employees.
+        _selectedEmployees.Add(employee)
     End Sub
 
+    ''' <inheritdoc/>
+    Public Sub RemoveEmployeeSelection(employee As IEmployee) Implements IEmployeeManager.RemoveEmployeeSelection
+        'Find the employee to remove.
+        Dim employeeToRemove = _selectedEmployees.Find(Function(selectedEmployee) selectedEmployee.Equals(employee))
+        If employeeToRemove Is Nothing Then
+            'The employee was not selected, thus can't be deselected.
+            Throw New Exception("Cannot remove the selection of a non-selected employee.")
+        End If
+        'Remove the employee.
+        _selectedEmployees.Remove(employeeToRemove)
+    End Sub
 End Class