Microsoft KB Archive/152071

= How to call a hidden default method of an OLE automation collection in Visual C++ =

Article ID: 152071

Article Last Modified on 11/21/2006

-

APPLIES TO

 Microsoft Foundation Class Library 4.2, when used with:  Microsoft Visual C++ 2.0 Professional Edition

 Microsoft Visual C++ 2.1

 Microsoft Visual C++ 2.2

 Microsoft Visual C++ 4.0 Standard Edition</li></ul>

 Microsoft Visual C++ 4.1 Subscription</li></ul>

 Microsoft Visual C++ 4.2 Enterprise Edition</li></ul>

 Microsoft Visual C++ 5.0 Enterprise Edition</li></ul>

 Microsoft Visual C++ 6.0 Enterprise Edition</li></ul>

 Microsoft Visual C++ 4.2 Professional Edition</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul> </li></ul>

-

<div class="notice_section">

This article was previously published under Q152071

<div class="summary_section">

SUMMARY
A technical article found on the Microsoft Developer Network CD-ROM titled "Implementing OLE Automation Collections," describes the functionality necessary to create an OLE automation collection. This includes creating a method called Item that returns the dispatch interface of the indicated item in the collection.

All OLE automation collection objects must implement the Item method to iterate through the objects of the collection. The implementation of the method might have been created hidden in the .ODL file for some applications. You cannot find these hidden methods by calling IDispatch::GetIdsOfNames. However, in many situations, this hidden method is the default method of the collection, in which case you can invoke it with an dispatch ID of DISPID_VALUE.

Visual Basic 3.0 depends on this Item method being the default method of the collection object.

<div class="moreinformation_section">

MORE INFORMATION
The following code sample illustrates using COleDispatchDriver::InvokeHelper to call the Item method from the Resources collection class provided by Microsoft Project 4.1. The Item method is hidden and cannot be found in the type library of the object:

Sample Code
void IterateCollection(void) {     Application App; // wrapper class for the 'Application' object Project Proj;   // wrapper class for the 'Project' object Resources Res;  // wrapper class for the 'Resources' object CString lpszFileName ("c:\\temp\\project2.mpp");

App.CreateDispatch("MSProject.Application");

VARIANT vFileName; VariantInit(&vFileName); V_VT(&vFileName) = VT_BSTR; V_BSTR(&vFileName) = lpszFileName.AllocSysString; App.FileOpen(vFileName);

Proj.AttachDispatch(App.GetActiveProject); Res.AttachDispatch(Proj.GetResources);

VARIANT vCount; VariantInit(&vCount); V_VT(&vCount) = VT_I4; vCount = Res.Count;

// the index of the collection starts with 1, not 0 for (int i = 1 ; i <= vCount.lVal ; i++) {        Resource r; // wrapper class for the 'Resource' object

VARIANT vResult, vIndex, vStr; VariantInit(&vResult); VariantInit(&vIndex); V_VT(&vIndex) = VT_I2; V_I2(&vIndex) = i;        static BYTE parms[] = VTS_VARIANT;

Res.InvokeHelper(DISPID_VALUE, DISPATCH_METHOD, VT_VARIANT,  (void*)&vResult, parms, &vIndex); r.AttachDispatch(vResult.pdispVal);

vStr = r.GetName; // ... 'vStr' now contains the Name property }  }

Additional query words: 2.00 2.10 2.20 4.00 4.10

Keywords: kbinfo kbautomation kbcode kbhowto KB152071

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.