Public Class Edu

    Public ReadOnly Property NoOfRegions() As Integer
        Get
            Return Regions.Count
        End Get
    End Property

    Public ReadOnly Property NoOfSchools() As Integer
        Get
            Dim C As Integer, Itm As Region
            For Each Itm In Regions
                C += Itm.NoOfSchools
            Next
            Return C
        End Get
    End Property

    Public ReadOnly Property NoOfStudents() As Integer
        Get
            Dim C As Integer, Itm As Region
            For Each Itm In Regions
                C += Itm.NoOfStudents
            Next
            Return C
        End Get
    End Property

    Public ReadOnly Regions As New RegionCollection()

    Public Class RegionCollection
        Inherits CollectionBase

        Friend Sub New()
            MyBase.New()
        End Sub

        Public Function Add(ByVal Name As String) As Region
            Dim R As New Region(Name)
            list.Add(R)
            Return R
        End Function

        Public Property Item(ByVal index As Integer) As Region

            Get
                If index > Count - 1 Or index < 0 Then
                    Dim Exc As New Exception("لا يوجد عنصر بهذا الرقم.")
                    Throw Exc
                Else
                    Return CType(List.Item(index), Region)
                End If
            End Get

            Set(ByVal Value As Region)
                If index > Count - 1 Or index < 0 Then
                    Dim Exc As New Exception("لا يوجد عنصر بهذا الرقم.")
                    Throw Exc
                Else
                    List.Item(index) = Value
                End If
            End Set

        End Property

        Public Sub Remove(ByVal Item As Region)
            List.Remove(Item)
        End Sub

    End Class

    Class Region
        Public Name As String
        Public ReadOnly Property NoOfSchools() As Integer
            Get
                Return Schools.Count
            End Get
        End Property
        Public ReadOnly Property NoOfStudents() As Integer
            Get
                Dim Itm As School, C As Integer
                For Each Itm In Schools
                    C += Itm.NoOfStudents
                Next
            End Get
        End Property
        Friend Sub New(ByVal Name As String)
            MyBase.New()
            Me.Name = Name
        End Sub

        Public ReadOnly Schools As SchoolCollection

        Public Class SchoolCollection
            Inherits CollectionBase

            Friend Sub New()
                MyBase.New()
            End Sub

            Public Function Add(ByVal Stage As School.Stages, ByVal Name As String) As School
                Dim S As New School(Stage, Name)
                list.Add(S)
                Return S
            End Function

            Public Property Item(ByVal index As Integer) As School

                Get
                    If index > Count - 1 Or index < 0 Then
                        Dim Exc As New Exception("لا يوجد عنصر بهذا الرقم.")
                        Throw Exc
                    Else
                        Return CType(List.Item(index), School)
                    End If
                End Get

                Set(ByVal Value As School)
                    If index > Count - 1 Or index < 0 Then
                        Dim Exc As New Exception("لا يوجد عنصر بهذا الرقم.")
                        Throw Exc
                    Else
                        List.Item(index) = Value
                    End If
                End Set

            End Property

            Public Sub Remove(ByVal Item As School)
                List.Remove(Item)
            End Sub

        End Class

        Public Class School

            Public ReadOnly Property NoOfStudents() As Integer
                Get
                    Return Students.Count
                End Get
            End Property
            Public Enum Stages
                ابتدائي
                إعدادي
                ثانوي
                صناعي
            End Enum

            Public Stage As Stages
            Public Name As String

            Friend Sub New(ByVal Stage As Stages, ByVal Name As String)
                MyBase.New()
                Me.Stage = Stage
                Me.Name = Name
            End Sub

            '-----------------------------------مجموعة الطلاب----------------------------
            Public ReadOnly Students As New StudentCollection(Stage)
            Public Class StudentCollection
                Inherits CollectionBase
                Dim Stage As Stages

                'Friend Sub New()
                '    MyBase.New()
                'End Sub

                Friend Sub New(ByVal Stage As Stages)
                    MyBase.New()
                    Me.Stage = Stage
                End Sub

                Public Function Add(ByVal Name As String, ByVal Year As Integer) As Student
                    Dim S As New Student(Name, Year, Stage)
                    list.Add(S)
                    Return S
                End Function

                Public Property Item(ByVal Index As Integer) As Student
                    Get
                        If Index > Count - 1 Or Index < 0 Then
                            Dim Exc As New Exception("لا يوجد عنصر بهذا الرقم.")
                            Throw Exc
                        Else
                            Return CType(List(Index), Student)
                        End If
                    End Get

                    Set(ByVal Value As Student)
                        If Index > Count - 1 Or Index < 0 Then
                            Dim Exc As New Exception("لا يوجد عنصر بهذا الرقم.")
                            Throw Exc
                        Else
                            List(Index) = Value
                        End If
                    End Set
                End Property

                Public Sub Remove(ByVal Item As Student)
                    list.Remove(Item)
                End Sub
            End Class

            ' ---------------------------------خليّة الطالب-------------------------------
            Public Class Student
                Public Name As String

                Dim Stage As Stages

                Friend Sub New(ByVal Name As String, ByVal Year As Integer, ByVal Stage As Stages)
                    MyBase.New()
                    Me.Name = Name
                    Me.Year = Year
                    Me.Stage = Stage
                End Sub

                Dim Yr As Integer
                Public Property Year() As Integer
                    Get
                        Return Yr
                    End Get
                    Set(ByVal Value As Integer)
                        Dim exc As New Exception("قيمة غير منطقيّة")
                        If Value < 1 And Value > 6 Then
                            Throw exc
                            Exit Property
                        End If

                        Select Case Stage
                            Case Stages.إعدادي, Stages.ثانوي, Stages.صناعي
                                If Value > 3 Then
                                    Throw exc
                                    Exit Property
                                End If
                        End Select
                        Yr = Value
                    End Set
                End Property
            End Class

        End Class

    End Class


End Class