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About S.Aziz
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All questions related to vb6 only. Excuse me for vb.net.

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You are here: Experts > Computing/Technology > Basic > Visual Basic > 2 level depth inheritance

Visual Basic - 2 level depth inheritance

Expert: S.Aziz - 10/28/2009

Question
Good day Sir. I just want to ask how to make a 2 level depth inheritance in VB6? Thank you for your time and God bless. Best regards.

Sincerely,

Josef Alarka

Answer
vb6 is not 100% Object Oriented but vb.net is. hereunder is a example of using inheritence (Treeview control) in vb6.

Option Explicit

Private WithEvents mTV As MSComctlLib.TreeView

Private m_bRectangleSelect As Boolean
Private m_x1 As Long, m_x2 As Long
Private m_y1 As Long, m_y2 As Long
Private m_bSingleSelect As Boolean
Private m_bSelectAll As Boolean
Private m_iShift As Integer
Private m_LastNode As MSComctlLib.Node

Event NodesSelected()

Public Property Let SingleSelect(ByVal bValue As Boolean)
m_bSingleSelect = bValue
End Property

Public Property Let SelectAll(ByVal bValue As Boolean)
m_bSelectAll = bValue
End Property

Public Property Set TV(tvValue As MSComctlLib.TreeView)
Set mTV = tvValue
End Property

Private Sub Class_Terminate()
Set mTV = Nothing
End Sub

Private Sub mTV_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If m_bSingleSelect Then Exit Sub

m_iShift = Shift

m_bRectangleSelect = False
m_x2 = -1

If (Button = vbLeftButton) Then
   If Shift = vbNormal Then
     If mTV.HitTest(X, Y) Is Nothing Then
       m_bRectangleSelect = True
       m_x1 = X / Screen.TwipsPerPixelX
       m_y1 = Y / Screen.TwipsPerPixelY
       m_x2 = -9
       mTV.Tag = "rect"
     End If
   End If
End If

End Sub

Private Sub mTV_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If m_bSingleSelect Then Exit Sub

If Button = vbLeftButton And Shift = vbNormal Then
   If m_x2 = -9 Or m_bRectangleSelect Then
     If m_x2 <> -9 Then
       DrawRectOnHwnd mTV.hWnd, m_x1, m_y1, m_x2, m_y2
     End If
     m_bRectangleSelect = True
     m_x2 = X / Screen.TwipsPerPixelX
     m_y2 = Y / Screen.TwipsPerPixelY
     DrawRectOnHwnd mTV.hWnd, m_x1, m_y1, m_x2, m_y2
   End If
End If
End Sub

Private Sub mTV_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
If m_bSingleSelect Then Exit Sub

If m_x2 >= 0 Then
   If Button = vbLeftButton And Shift = vbNormal Then
     If m_bRectangleSelect Then
       RectangleSelect mTV
       mTV.Refresh
     End If
   End If
End If
mTV.Tag = ""
m_bRectangleSelect = False
m_x2 = -1
End Sub

Private Sub RectangleSelect(myTV As MSComctlLib.TreeView)
If Not m_bRectangleSelect Then Exit Sub

TVRectangleSelect myTV, m_x1, m_x2, m_y1, m_y2, m_bSelectAll
RaiseEvent NodesSelected
End Sub

Private Sub SelectShift()
Dim curNode As MSComctlLib.Node
Dim bOK As Boolean

If mTV.Nodes.Count > 0 Then
   Set curNode = m_LastNode

   Do
     If Len(curNode.Tag) > 0 Then
       If curNode.Key = m_LastNode.Key Then bOK = True
       If bOK Then
         curNode.BackColor = vbHighlight
         curNode.ForeColor = vbHighlightText
       End If
       If curNode.Key = mTV.SelectedItem.Key Then bOK = False
     End If
     Set curNode = curNode.Next
   Loop Until curNode Is Nothing
End If

End Sub

Private Sub mTV_NodeClick(ByVal Node As MSComctlLib.Node)
Dim curNode As MSComctlLib.Node

If Len(Node.Tag) = 0 Then Exit Sub

Select Case m_iShift

   Case vbNormal
     Set m_LastNode = Node

     With mTV
       If .Nodes.Count > 0 Then
         For Each curNode In .Nodes
           curNode.BackColor = vbWindowBackground
           curNode.ForeColor = vbButtonText
         Next
       End If
     End With

   Case vbShiftMask
     If Not m_LastNode Is Nothing Then
       If Not mTV.SelectedItem Is Nothing Then
         SelectShift
       End If
     End If
     Set m_LastNode = Nothing

   Case vbCtrlMask
     Set m_LastNode = Nothing

End Select

Node.BackColor = vbHighlight
Node.ForeColor = vbHighlightText

m_iShift = 0
End Sub

*******In the desired form add a reference to the control********

Private WithEvents m_ctvFrom As clsTreeView

Private Sub Form_Load()
Set m_ctvFrom = New clsTreeView
Set m_ctvFrom.TV = tvFrom ' <- The real TreeView
End Sub

Private Sub Form_Unload(Cancel As Integer)
Set m_ctvFrom.TV = Nothing
Set m_ctvFrom = Nothing
End Sub

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