Q141414: HOWTO: Enumerate OLE and VB Controls from an OLE Control
Article: Q141414
Product(s): Microsoft Visual Basic for Windows
Version(s): 2.0,2.1,2.2,4.0,5.0,6.0
Operating System(s):
Keyword(s): kbActiveX kbCOMt kbCtrlCreate kbMFC kbVBp400 kbVBp500 kbVBp600 kbVC200 kbVC400 kbVC500
Last Modified: 07-MAY-2001
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual Basic Professional Edition for Windows, version 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0
- Microsoft Visual C++, versions 2.0, 2.1, 2.2, 4.0
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
-------------------------------------------------------------------------------
SUMMARY
=======
For an OLE control to communicate with another control placed on the same Visual
Basic form, the OLE control needs access to at least one interface pointer of
the other control. This article illustrates a technique you can use to enumerate
both OLE and Visual Basic controls present on a particular form and retrieve an
interface pointer to these controls. Note that the same technique could be
applied to enumerate controls placed on other control containers, provided that
container exposes the functionality required to implement the technique.
MORE INFORMATION
================
Given a pointer to IOleClientSite, it is possible to enumerate through all of
the other controls on a form by making use of the following interfaces:
IOleClientSite
IOleContainer
IEnumUnknown
IUnknown
IOleObject
IOleClientSite
IOleControlSite
Note that most of these interfaces are container-side interfaces, so the
technique mentioned here is container dependent. For this method to work, the
container must provide support for IOleContainer, which is currently defined as
a mandatory interface in the OLE control container guidelines. Both MFC version
4.0 and greater and Visual Basic version 4.0 and greater OLE control containers
provide support for this interface. Before using this method with another
control container, ensure that it provides support for IOleContainer.
The method itself is illustrated by the sample code listed in this article. You
can incorporate the code into an OLE control generated using ControlWizard. Use
the code to enumerate all the controls, internal Visual Basic controls as well
OLE controls, by calling IOleContainer::EnumObjects, and passing the following
flags as its first parameter:
OLECONTF_EMBEDDINGS: is used to retrieve OLE Controls.
OLECONTF_OTHERS : is used to retrieve other objects such as Visual
Basic internal controls.
hr = lpContainer->EnumObjects(OLECONTF_EMBEDDINGS | OLECONTF_OTHERS,
&lpEnumUnk);
The differentiating aspect between OLE controls and other objects such as
internal Visual Basic controls is that only OLE controls support the IOleObject
interface. Hence, if a QueryInterface for IID_IOleObject fails for an object,
then it is a different type of object. Also, if the control container provides
support for Extended controls as does Visual Basic 4.0, the Extended control for
a particular OLE control can also be retrieved using the method illustrated by
the sample code.
Note that most of the functionality provided by the following sample code depends
solely on the extent of the functionality exposed by the control container
itself.
Also note that the LPOLECLIENTSITE pointer can be obtained through a call to
COleControl::GetClientSite().
Sample Code
-----------
void EnumAllControlNames(LPOLECLIENTSITE lpSite)
{
LPOLECONTAINER lpContainer;
LPENUMUNKNOWN lpEnumUnk;
// Note that the IOleContainer interface is currently defined as
// mandatory. It must be implemented by control containers,
// in the OLE Control Containers Guidelines.
HRESULT hr = lpSite->GetContainer(&lpContainer);
if(FAILED(hr)) {
OutputDebugString(_T("Unable to get to the container.\n"));
return;
}
// OLECONTF_EMBEDDINGS is used to retrieve OLE Controls.
// OLECONTF_OTHERS is used to retrieve other objects such as
// Visual Basic internal controls
hr = lpContainer->EnumObjects(
OLECONTF_EMBEDDINGS | OLECONTF_OTHERS,
&lpEnumUnk);
if(FAILED(hr)) {
lpContainer->Release();
return;
}
LPUNKNOWN lpUnk;
while (lpEnumUnk->Next(1, &lpUnk, NULL) == S_OK) {
LPOLEOBJECT lpObject = NULL;
LPOLECONTROLSITE lpTargetSite = NULL;
LPOLECLIENTSITE lpClientSite = NULL;
LPDISPATCH lpDisp;
hr = lpUnk->QueryInterface(
IID_IOleObject, (LPVOID*)&lpObject);
if(SUCCEEDED(hr)) {
// This is an OLE control.
// Navigate to the Extended Control because Visual Basic 4.0 uses
// Extended controls.
hr = lpObject->GetClientSite(&lpClientSite);
if(SUCCEEDED(hr)) {
// You have the IOleClientSite interface
hr = lpClientSite->QueryInterface(
IID_IOleControlSite, (LPVOID*)&lpTargetSite);
if(SUCCEEDED(hr)) {
// You have the IOleControlSite interface
// Get the IDispatch for the extended control.
// Note that Extended controls are optional in the OLE
// specifications for OLE Control Containers.
hr = lpTargetSite->GetExtendedControl(&lpDisp);
}
}
}
else {
// This is either an internal VB control or the
// VB form itself.
hr = lpUnk->QueryInterface(
IID_IDispatch, (LPVOID*)&lpDisp);
}
if(SUCCEEDED(hr)) {
VARIANT va;
VariantInit(&va);
DISPID dispid;
DISPPARAMS dispParams = { NULL, NULL, 0, 0 };
// Get the names of all the controls present in a VB form.
LPWSTR lpName[1] = { (WCHAR *)L"Name" };
hr = lpDisp->GetIDsOfNames(IID_NULL, lpName, 1,
LOCALE_SYSTEM_DEFAULT, &dispid);
if(SUCCEEDED(hr)) {
hr = lpDisp->Invoke(dispid/*0x80010000*/, IID_NULL,
LOCALE_SYSTEM_DEFAULT,
DISPATCH_PROPERTYGET |
DISPATCH_METHOD,
&dispParams, &va, NULL, NULL);
if(SUCCEEDED(hr)) {
CString szTmp((LPCWSTR)va.bstrVal);
// szTmp now has the name.
OutputDebugString(_T("And the name is ... ") + szTmp +
_T("\n"));
}
}
lpDisp->Release();
}
// Release interface pointers.
if(lpObject) lpObject->Release();
if(lpTargetSite) lpTargetSite->Release();
if(lpClientSite) lpClientSite->Release();
lpUnk->Release();
} // End of While statement
// Final clean up
lpEnumUnk->Release();
lpContainer->Release();
}
Additional words: VB VC visualc cdk ocx
Additional query words:
======================================================================
Keywords : kbActiveX kbCOMt kbCtrlCreate kbMFC kbVBp400 kbVBp500 kbVBp600 kbVC200 kbVC400 kbVC500 kbVC600 kbGrpDSMFCATL
Technology : kbVCsearch kbVC400 kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600 kbVC220 kbVC500 kbVC600 kbVC200 kbVC210 kbVC32bitSearch kbVC500Search
Version : :2.0,2.1,2.2,4.0,5.0,6.0
Issue type : kbhowto
=============================================================================
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
Copyright Microsoft Corporation 1986-2002.