>-----Original Message-----
>Hi,
>
>I have a problem when an unmanaged C++ client gets a COM
>object from a C# server, which it in turn has got from a
>COM server. It works 75% of the time, but sometimes it
>crashes.
>
>The COM .exe server's idl looks something like:
>
>[
> object,
> uuid(F534D8C9-033A-4E17-B73A-440B6BE7B5EB),
> dual,
> nonextensible,
> pointer_default(unique)
>]
>interface IItem : IDispatch
>{
>};
>
>[
> object,
> uuid(158E2223-4973-4231-A51C-34B49B16858D),
> dual,
> nonextensible,
> pointer_default(unique)
>]
>interface ICollection : IDispatch
>{
> [propget, id(1)] HRESULT Count([out, retval] long*
>pVal);
> [id(2)] HRESULT Add([in] IItem* pItem);
> [propget, id(DISPID_VALUE)] HRESULT Item([in] long
>Index, [out, retval] VARIANT* pVal);
> [propget, id(DISPID_NEWENUM)] HRESULT _NewEnum
>([out, retval] LPUNKNOWN* pVal);
>};
>
>[
> object,
> uuid(9E97E74D-6A36-4218-933A-D7DCAC802F61),
> dual,
> nonextensible,
> pointer_default(unique)
>]
>interface IManager : IDispatch
>{
> [id(4)] HRESULT GetCollection([in] BSTR someBstr,
>[in] BSTR anotherBstr, [out,retval] ICollection** menu);
>};
>
>[
> uuid(B7A4DD8D-E760-46D2-A699-A623290CE005),
> version(1.0),
>]
>library LIBRARYLib
>{
> importlib("stdole32.tlb");
> importlib("stdole2.tlb");
>
> [
> uuid(FF23BFD1-1C9F-487C-8754-0926810DEBD5),
> ]
> coclass Manager
> {
> [default] interface IManager;
> };
>
> [
> uuid(08E1F10A-24E8-4037-96C3-ED5BB61531A3),
> ]
> coclass Collection
> {
> [default] interface ICollection;
> };
> [
> uuid(303AF813-528F-4B6D-B297-517CA6DB0EC5),
> ]
> coclass Item
> {
> [default] interface IItem;
> };
>};
>
>The GetCollection method creates some items and puts them
>in a collection.
>
>This is then exposed to .Net using:
>Tlbimp MyCOMExe.exe /out:MyCOMExe.dll
>
>MyCOMExe.dll is referenced in a C# project. The C# code
>looks something like:
>
>using System;
>using System.Runtime.InteropServices;
>using System.Reflection;
>using MyCOMExe;
>
>namespace MyDotNet
>{
> [InterfaceType
>(ComInterfaceType.InterfaceIsIDispatch), Guid("58E50811-
>9733-412a-8BFA-9B4960E3467A")]
> public interface _DotNetManager
> {
> [return:MarshalAs
>(UnmanagedType.IDispatch)] Object GetCollection(string
>someString, Object someObject);
> }
>
> [ClassInterface(ClassInterfaceType.None), Guid
>("85A834FC-BE33-440e-95A5-40EE78E80693")]
> public class DotNetManager : _DotNetManager
> {
> [return:MarshalAs(UnmanagedType.IDispatch)]
>public Object GetCollection(string someString, Object
>someObject)
> {
> Manager mgr = new Manager();
>
> // do some stuff
> // Get some stuff from a database
> // etc.
>
> Collection coll = mgr.GetCollection
>(someString, abotherString);
> return coll;
> }
> }
>}
>
>The above is regisetered for COM interop.
>Then, in an unmanaged MFC C++ client, I have a header
file
>similar to:
>
>// Dlg.h
>#pragma once
>#include "afxwin.h"
>
>#include "TheHeaderFileForMyCOMExe.h"
>#import "MyDotNet.tlb"
>
>using namespace MyDotNet;
>
>class CDlg : public CDialog
>{
>public:
> CDlg(CWnd* pParent = NULL);
>// ...
> protected:
> virtual void DoDataExchange(CDataExchange* pDX);
> // DDX/DDV support
>
>// Implementation
>protected:
>// etc. etc.
>public:
> afx_msg void OnBnClickedButton1();
> afx_msg void OnBnClickedButton2();
>
>private:
> _DotNetManager* pDot;
> CComPtr<ICollection> pCollection;
>};
>
>and a CPP file something like:
>
>// Dlg.cpp
>#include "stdafx.h"
>#include "CPPTest.h"
>#include "Dlg.h"
>
>#include "MyCOMExe_i.c"
>
>// ...
>
>
>void CCPPTestDlg::OnBnClickedButton1()
>{
> _DotNetManagerPtr p(__uuidof(DotNetManager));
> pDot = p;
>}
>
>void CCPPTestDlg::OnBnClickedButton2()
>{
> // Release old collection if necessary:
> if (pCollection)
> {
> pCollection.Release();
> pCollection = NULL;
> }
>
> // yada yada yada
>
> IDispatch* pDisp = NULL;
>
> pDisp = pDot->GetCollection
>(someCString.AllocSysString(), someObjectPtr);
> HRESULT hr = pDisp->QueryInterface
>(IID_ICollection, (void**)&pCollection);
> pDisp->Release();
>
> // Get enumerator for Collection
> LPUNKNOWN punkEnum;
> hr = pCollection->get__NewEnum(&punkEnum) ;
> IEnumVARIANT* pEnum;
>
> hr = punkEnum->QueryInterface(&pEnum);
> punkEnum->Release();
>
> VARIANT vntNext;
> VariantInit(&vntNext);
>
> // Get the number of items in menu:
> long count = 0;
> hr = pContextMenu->get_Count(&count);
>
> // Do something with each item:
> for (int i = 0; i < count; i++)
> {
> // Get the next item in the collection
> hr = pEnum->Next(1, &vntNext, NULL);
> CComQIPtr<IItem> pItem(vntNext.pdispVal);
>
> // do something with the item
> }
>}
>
>OnBnClickedButton1() is called once, and then
>OnBnClickedButton2() is called repeatedly. It always
works
>the first time OnBnClickedButton2 is called. Sometimes
the
>second time causes a crash, sometimes the third time, etc.
>(Incidentally, from a VB client it never crashes).
>When it crashes, I get the following output:
>First-chance exception at 0x779db680 in CPPTest.exe:
>0xC0000005: Access violation reading location 0xcccccccc.
>Unhandled exception at 0x779db680 in CPPTest.exe:
>0xC0000005: Access violation reading location 0xcccccccc.
>First-chance exception at 0x779db680 in CPPTest.exe:
>0xC0000005: Access violation reading location 0xcccccccc.
>Unhandled exception at 0x779db680 in CPPTest.exe:
>0xC0000005: Access violation reading location 0xcccccccc.
>First-chance exception at 0x779db680 in CPPTest.exe:
>0xC0000005: Access violation reading location 0xcccccccc.
>Unhandled exception at 0x779db680 in CPPTest.exe:
>0xC0000005: Access violation reading location 0xcccccccc.
>The program '[3336] CPPTest.exe: Native' has exited with
>code 0 (0x0).
>The program '[3336] CPPTest.exe: DefaultDomain' has
exited
>with code 0 (0x0).
>
>and the debugger points to a location in the MyDotNet.tli
>file, which looks like:
>inline IDispatchPtr _DotNetManager::GetCollection (
>_bstr_t someBstr, const _variant_t & someObject ) {
> IDispatch * _result = 0;
> _com_dispatch_method(this, 0x60020000,
>DISPATCH_METHOD, VT_DISPATCH, (void*)&_result,
> L"\x0008\x000c", (BSTR)someBstr,
&someObject ); //
>this is the line the debugger points to
> return IDispatchPtr(_result, false);
>
>Any ideas as to what may cause this behaviour would be
>greatly appreciated.
>
>Best regards,
>Lars
>.