INFO: The Type of OCX Property in Typelib Should Match Its RetVal (153632)
The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows 6.0
- Microsoft Visual Basic Professional Edition for Windows 6.0
- Microsoft Visual Basic Enterprise Edition for Windows 6.0
- Microsoft Visual Basic Control Creation Edition for Windows 5.0
- Microsoft Visual Basic Learning Edition for Windows 5.0
- Microsoft Visual Basic Professional Edition for Windows 5.0
- Microsoft Visual Basic Enterprise Edition for Windows 5.0
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows 4.0
This article was previously published under Q153632 SUMMARY
An ActiveX control can cause an unhandled exception in VB32.exe if the
type of any of its Properties as specified in its ODL file differs from the
actual type that the property handler returns.
MORE INFORMATION
For example, this will happen if, in an ActiveX control's type library, a
property is marked as type String (VT_BSTR), and the Get method for this
property returns an integer (VT_I4). This is because when Visual Basic
calls IDispatch::Invoke() to get that property value, the control fills in
the Result variant parameter of Invoke() with the type VT_I4, but Visual
Basic believing it is a string (from the Typelib definition), tries to
dereference the integer and hence the general protection (GP) fault. Visual
Basic assumes that the type returned by Invoke() will be the same as the
type stated in the type library.
This situation can be prevented by fixing the type library of the custom
OLE control or the property handler for the related property, whichever is
wrong.
| Modification Type: | Minor | Last Reviewed: | 7/16/2004 |
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| Keywords: | kbinfo KB153632 |
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