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POExposing COM events to VBScript (ATL)
 

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    <p>I have built a COM server DLL in C++ with ATL by using the "ATL simple object" wizard. I followed Microsoft's <a href="http://code.msdn.microsoft.com/windowsdesktop/ATLDllCOMServer-09df00e4" rel="nofollow noreferrer">ATLDLLCOMServer</a> example. Everything works well except for one thing: <strong>I do not receive COM events in VBScript</strong>. I do receive the events in C#. I had events working in VBScript in an earlier MFC-based implementation as ActiveX control.</p> <p>My control is defined like this:</p> <pre><code>class ATL_NO_VTABLE CSetACLCOMServer : public CComObjectRootEx&lt;CComSingleThreadModel&gt;, public CComCoClass&lt;CSetACLCOMServer, &amp;CLSID_SetACLCOMServer&gt;, public IConnectionPointContainerImpl&lt;CSetACLCOMServer&gt;, public CProxy_ISetACLCOMServerEvents&lt;CSetACLCOMServer&gt;, public IDispatchImpl&lt;ISetACLCOMServer, &amp;IID_ISetACLCOMServer, &amp;LIBID_SetACLCOMLibrary, /*wMajor =*/ 1, /*wMinor =*/ 0&gt;, public IProvideClassInfo2Impl&lt;&amp;CLSID_SetACLCOMServer, &amp;DIID__ISetACLCOMServerEvents, &amp;LIBID_SetACLCOMLibrary&gt; /* Required for event support in VBS */ { public: BEGIN_COM_MAP(CSetACLCOMServer) COM_INTERFACE_ENTRY(ISetACLCOMServer) COM_INTERFACE_ENTRY(IDispatch) COM_INTERFACE_ENTRY(IConnectionPointContainer) COM_INTERFACE_ENTRY(IProvideClassInfo) COM_INTERFACE_ENTRY(IProvideClassInfo2) END_COM_MAP() BEGIN_CONNECTION_POINT_MAP(CSetACLCOMServer) CONNECTION_POINT_ENTRY(__uuidof(_ISetACLCOMServerEvents)) END_CONNECTION_POINT_MAP() [...] </code></pre> <p>In VBScript I use the COM object like this:</p> <pre><code>set objSetACL = WScript.CreateObject("SetACL.SetACL", "SetACL_") ' Catch and print messages from the SetACL COM server which are passed (fired) as events. ' The name postfix of this function (MessageEvent) must be identical to the event name ' as defined by SetACL. ' The prefix (SetACL_) can be set freely in the call to WScript.CreateObject sub SetACL_MessageEvent (Message) WScript.Echo Message end sub </code></pre> <p>The relevant parts of the IDL look like this:</p> <pre><code>[ object, uuid(E1B57CA5-FD7F-4304-BC0A-8BEBDE231D53), dual, nonextensible, pointer_default(unique), helpstring("SetACL COM Interface") ] interface ISetACLCOMServer : IDispatch { }; [ uuid(00D4DCD3-02B9-4A71-AB61-2283504620C8), version(1.0), helpstring ("SetACL Type Library") ] library SetACLCOMLibrary { importlib("stdole2.tlb"); [ uuid(35F76182-7F52-4D6A-BD6E-1317345F98FB), helpstring ("SetACL Event Interface") ] dispinterface _ISetACLCOMServerEvents { properties: methods: [id(1), helpstring("Receives string messages that would appear on the screen in the command line version")] void MessageEvent([in] BSTR message); }; [ uuid(13379563-8F21-4579-8AC7-CBCD488735DB), helpstring ("SetACL COM Server"), ] coclass SetACLCOMServer { [default] interface ISetACLCOMServer; [default, source] dispinterface _ISetACLCOMServerEvents; }; }; </code></pre> <p>The <strong>problem</strong>: SetACL_MessageEvent never gets called.</p> <p>What I have tried:</p> <ul> <li>After reading <a href="http://support.microsoft.com/default.aspx?scid=kb;en-us;200839" rel="nofollow noreferrer">this KB article</a> I added the implementation of IProvideClassInfo2, but that did not help.</li> <li>This <a href="http://support.microsoft.com/kb/166480" rel="nofollow noreferrer">FAQ</a> mentions that outgoing interface should not defined as a dual interfaces. I removed the "dual" from my interface definition, but that did not help.</li> <li>I found <a href="https://stackoverflow.com/questions/9170054/atl-com-events-for-javascript">this SO question</a> that seems to describe a similar problem. An answer was never given, only a workaround.</li> </ul> <p><strong>UPDATE 1:</strong></p> <p>I know now where it is failing, but not why: in the fire event method in _ISetACLCOMServerEvents_CP.h the call to Invoke fails with E_UNEXPECTED. This is the line:</p> <pre><code>hr = pConnection-&gt;Invoke(1, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_METHOD, &amp;params, NULL, NULL, NULL); </code></pre> <p><strong>Solution:</strong></p> <p>The problem was that I called the event firing function from a background thread in the COM object, in other words from the wrong apartment.</p>
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    1. USHelge Klein
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    1. CODon't you have to use `WithEvents` in vbscript/vba to be able to respond to COM events ?
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      1. POExposing COM events to VBScript (ATL)
      1. USAlexandre C.
    2. CONo, according to http://msdn.microsoft.com/en-us/library/ms974564.aspx you do not.
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      1. USHelge Klein
    3. COI think you lost 2nd parameter in `IProvideClassInfo2Impl`. I should have been the events interface `IID`.
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      1. USRoman R.
 

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