Use ByVal to Pass a Control as an Argument to a DLL or VBX (129827)
The information in this article applies to:
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows 4.0
- Microsoft Visual Basic Professional Edition, 16-bit, for Windows 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows 4.0
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows 4.0
This article was previously published under Q129827
In previous versions of Visual Basic, when you passed a control to a DLL or
VBX, your function declaration looked like this:
Declare Function fDoNothing Lib "MyFun.vbx" (ctlX as Control) As Integer
Now, in Microsoft Visual Basic version 4.0, the keyword ByVal must
be used when passing the same control, so now your function declaration
must look like this:
Declare Function fDoNothing Lib "MyFun.vbx" (ByVal ctlX as Control)_
As Integer
The Visual Basic API was changed. Now, functions expecting a control as a
parameter require a handle to the control, an HCTL. Omitting ByVal within
the parameter list causes a pointer to the HCTL to be passed instead of the
HCTL itself. To ensure an HCTL is passed, use the ByVal keyword. This
behavior is by design.
| Modification Type: | Major | Last Reviewed: | 12/9/2003 |
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| Keywords: | KB129827 |
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