Visual Basic Programming Code Examples

Visual Basic > Forms Code Examples

Unload all forms currently in memory

Unload all forms currently in memory

One of the fundamental weeknesses with many VB applications is the lack of explicit unloading of unload objects. When dealing with forms, many programmers unload every form in a project on it's termination, even if only a few of the forms are actually loaded. This will cause the forms that aren't loaded to be loaded then unloaded, which may create further complications. The following code demonstrates how to explicitly unload all the forms currently in memory and even unloads them in the correct order, which is neccessary if modal forms are present. Note, two versions of this code have been supplied, one for VBA programmers and one for VB programmers.


VBA ROUTINE
-----------------------

Option Explicit
Private Declare Function GetActiveWindow Lib "user32" () As Long
Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long

'Purpose     :  This routine unloads all forms in memory for this project.
'Inputs      :  bFormsModal                 If True the application contains modal forms and
'                                           hence form the topmost first
'Outputs     :  Returns True if all the forms where successfully unloaded.


Function FormsSafeUnload(Optional bFormsModal As Boolean = True) As Boolean
    Dim lForm As Long, fForm As Object, lLoopCount As Long, lActiveWindow As Long
    Dim sActiveCaption As String
    
    On Error GoTo ErrFailed
    
    If bFormsModal Then
        'Unload all visible forms from topmost first.
        'Note: cannot loop as uses the active window
        lActiveWindow = GetActiveWindow
        Do While lActiveWindow
            sActiveCaption = DialogGetCaption(lActiveWindow)
            For lForm = VBA.UserForms.Count - 1 To 0 Step -1
                If VBA.UserForms(lForm).Caption = sActiveCaption Then
                    'Found topmost form, unload it
                    '(Can add break point on line below)
                    Unload VBA.UserForms(lForm)
                End If
            Next
            lActiveWindow = GetActiveWindow
            If VBA.UserForms.Count = 0 Then
                Exit Do
            ElseIf lForm = -1 Then
                'Failed to find active form
                '(Make sure you are not debugging this loop)
                Exit Do
            End If
        Loop
    End If
    
    'Unload forms (including hidden forms)
    For Each fForm In VBA.UserForms
        Unload fForm
    Next

    FormsSafeUnload = (VBA.UserForms.Count = 0)
    Exit Function
    
ErrFailed:
    FormsSafeUnload = False
End Function

'Purpose     :  Returns the window caption of a specified window.
'Inputs      :  lHwnd                       The handle of the window to determine the caption of.
'Outputs     :  Returns the window caption of a specified window.


Function DialogGetCaption(lHwnd As Long) As String
    Const clMaxLen As Long = 255
    Dim lLen As Long, sValue As String * clMaxLen
    
    lLen = GetWindowText(lHwnd, sValue, clMaxLen)
    If lLen Then
        DialogGetCaption = Left$(sValue, lLen)
    End If
End Function




VB ROUTINE
----------

Option Explicit
Private Declare Function GetActiveWindow Lib "user32" () As Long

'Purpose     :  This routine unloads all forms in memory for this project.
'Inputs      :  bFormsModal                 If True the application contains modal forms and
'                                           hence form the topmost first
'Outputs     :  Returns True if all the forms where successfully unloaded.


Function FormsSafeUnload(Optional bFormsModal As Boolean = True) As Boolean
    Dim lForm As Long, fForm As Form, lLoopCount As Long, lActiveWindow As Long
    
    On Error GoTo ErrFailed
    
    If bFormsModal Then
        'Unload all visible forms from topmost first.
        'Note: cannot loop as uses the active window
        lActiveWindow = GetActiveWindow
        Do While lActiveWindow
            For lForm = VB.Forms.Count - 1 To 0 Step -1
                If VB.Forms(lForm).hWnd = lActiveWindow Then
                    'Found topmost form, unload it
                    '(Can add break point on line below)
                    Unload VB.Forms(lForm)
                End If
            Next
            lActiveWindow = GetActiveWindow
            If VB.Forms.Count = 0 Then
                Exit Do
            ElseIf lForm = -1 Then
                'Failed to find active form
                '(Make sure you are not debugging this loop)
                Exit Do
            End If
        Loop
    End If
    
    'Unload forms (including hidden forms)
    For Each fForm In VB.Forms
        Unload fForm
    Next

    FormsSafeUnload = (VB.Forms.Count = 0)
    Exit Function
    
ErrFailed:
    FormsSafeUnload = False
End Function