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| Title | Make a TextBox accept only digits |
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| Keywords | TextBox, only digits, numeric field |
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| Categories | Controls |
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Use the SetWindowLong API function to set the TextBox's extended style to include
ES_NUMBER. Then subclass the control to monitor its messages.
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Private Sub Form_Load()
Dim style As Long
' Get the current style.
style = GetWindowLong(Text1.hWnd, GWL_STYLE)
' Add ES_NUMBER to the style.
SetWindowLong Text1.hWnd, GWL_STYLE, style Or ES_NUMBER
' Subclass to ignore the context menu.
OldWindowProc = SetWindowLong( _
Text1.hWnd, GWL_WNDPROC, _
AddressOf NewWindowProc)
End Sub
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The new WindowProc ignores the WM_CONTEXTMENU message which drops down the control's context menu.
Through that menu the user could paste non-digits into the TextBox.
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' Pass along all messages except the one that makes the
' context menu appear.
Public Function NewWindowProc(ByVal hWnd As Long, ByVal msg _
As Long, ByVal wParam As Long, ByVal lParam As Long) As _
Long
If msg <> WM_CONTEXTMENU Then _
NewWindowProc = CallWindowProc( _
OldWindowProc, hWnd, msg, wParam, _
lParam)
End Function
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Note that my book Custom Controls Library shows how to make field controls that
do this sort of thing.
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