可以公开用 C# 编写的托管事件，以便在使用 c++ 编写的 COM 对象中公开和使用。对com和atl不太熟悉。对于 MSDN 文章中显示的示例，您能否展示一下 C++ 方面的情况
http://msdn.microsoft.com/en-us/library/dd8bf0x3.aspx
显示的VB6代码证明它是可行的。
【问题讨论】：
如果您可以使用 C++/CLI，您可以这样做 (source)：
// class that defines methods that will called when event occurs
ref class EventReceiver {
public:
void OnMyClick(int i, double d) {
Console::WriteLine("OnClick: {0}, {1}", i, d);
}
void OnMyDblClick(String^ str) {
Console::WriteLine("OnDblClick: {0}", str);
}
};
int main() {
EventSource ^ MyEventSource = gcnew EventSource();
EventReceiver^ MyEventReceiver = gcnew EventReceiver();
// hook handler to event
MyEventSource->OnClick += gcnew ClickEventHandler(MyEventReceiver, &EventReceiver::OnMyClick);
}
【讨论】：
IMO 中最简单的 C++ 方法是借助 ATL 的 IDispEventImpl 和 IDispEventSimpleImpl 模板实现事件接收器。示例项目can be found here的解释。
有很多关于如何做到这一点的在线资源，例如this 或 this，但这里是所需步骤的列表：
首先让我们看一下托管端。
为了提供事件，我们必须做到以下几点：
ComSourceInterfaces属性标记coclass，将事件接口绑定到coclass这里是托管代码：
[ComVisible(true),
Guid("D6D3565F-..."),
InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] //! must be IDispatch
public interface IMyEvents
{
[DispId(1)] // the dispid is used to correctly map the events
void SomethingHappened(DateTime timestamp, string message);
}
[ComVisible(true)]
[Guid("E22E64F7-...")]
[ProgId("...")]
[ClassInterface(ClassInterfaceType.None)]
[ComSourceInterfaces(typeof(IMyEvents))] // binding the event interface
public class MyComServer : IMyComServer
{
// here we declare the delegate for the event
[ComVisible(false)]
public delegate void MyEventHandler(DateTime timestamp, string message);
// and a public event which matches the method in IMyEvents
// your code will raise this event when needed
public event MyEventHandler SomethingHappened;
...
}
现在，回到非托管方面。我将使用 ATL，因为我发现它是编写 COM 客户端的最有效方式，但您可以尝试 MFC 或“手动”进行。
需要以下步骤：
IDispEventSimpleImpl（或IDispEventImpl）这是 ATL C++ 客户端中的代码：
// import the typelib of your COM server
// 'named_guids' ensures friendly ID of event interface
#import "myserver.tlb" named_guids
const UINT SINK_ID = 234231341; // we need some sink id
class MyClient : public IDispEventSimpleImpl<SINK_ID, MyClient, &MyServer::DIID_IMyEvents >
{
public:
// now you need to declare a sink map - a map of methods handling the events
BEGIN_SINK_MAP(MyClient)
SINK_ENTRY_INFO(SINK_ID, MyServer::DIID_IMyEvents, 0x1, OnSomethingHappened, &someEvent)
^ ^ ^ ^
// event interface id (can be more than 1)---+ | | |
// must match dispid of your event -----------------+ | |
// method which handles the event ------------------------+ |
// type information for event, see below --------------------------------------+
END_SINK_MAP()
// declare the type info object. You will need one for each method with different signature.
// it will be defined in the .cpp file, as it is a static member
static _ATL_FUNC_INFO someEvent; // 'placeholder' object to carry event information (see below)
// method which handles the event
STDMETHOD (OnSomethingHappened)(DATE timestamp, BSTR message)
{
// usually it is defined it in the .cpp file
}
...
}
现在，我们需要在 cpp 文件中定义类型信息成员（即上面示例中的 someEvent 实例）：
_ATL_FUNC_INFO MyClient::traceEvent = { CC_STDCALL, VT_EMPTY, 2 , {VT_DECIMAL, VT_BSTR} }; // dispid = 1
^ ^ ^ ^
// calling convention (always stdcall) --------+ | | |
// type of return value (only VT_EMPTY makes sense) ----+ | |
// number of parameters to the event -------------------------+ |
// Variant types of event arguments -----------------------------------------+
这可能会很棘手，因为类型映射并不总是很明显（例如，很明显托管 int 映射到 VT_I4，但不太明显 DateTime 映射到 VT_DECIMAL）。
您需要在接收器映射中声明您计划使用的每个事件 - 如果您不需要所有事件，请不要映射它们。
现在您需要将接收器连接到事件源：
// IUnknown* pUnk = interface to you COM server instance
pMyClient->DispEventAdvise(pUnk);
// .. from this point, events will be caught by the client
// when you are done, disconnect:
pMyClient->DispEventUnadvise(pUnk);
差不多就是这样。使用IDispEventImpl 而不是IDispEventSimpleImpl 会产生更少的代码，因为您不需要提供可能是最难看的部分的类型信息对象。但是，它有两个缺点：
【讨论】：
Zdeslav Vojkovic 提出的解决方案对我来说几乎是完整的答案，但是在 Outlook 加载项中实施接收器时遇到了稳定性问题。在第一次不建议之后，系统变得不稳定，并且可能在下一次建议时崩溃。我的解决方案是将接收器作为 COM 对象。
为简洁起见，我只添加了解决方案的 ATL 方面，因为托管代码可以完全按照 Zdeslav Vojkovic 的建议保留。
我在 Visual Studio 2017 中按照以下步骤操作：
在生成的 idl 中添加用于初始化和关闭的处理程序：
[
object,
uuid(a5211fba-...),
dual,
nonextensible,
pointer_default(unique)
]
interface IMyClient : IDispatch
{
[id(1), helpstring("method InitHandler"), local] HRESULT InitHandler(IUnknown* myserver);
[id(2), helpstring("method ShutdownHandler"), local] HRESULT ShutdownHandler(void);
};
const UINT SINK_ID = 234231341;
extern _ATL_FUNC_INFO SomethingHappenedInfo;
// LIBID_MyATLComLib should point to the LIBID of the type library
class ATL_NO_VTABLE CMyClient :
public CComObjectRootEx<CComSingleThreadModel>,
public CComCoClass<CMyClient, &CLSID_MyClient>,
public IDispatchImpl<IMyClient, &IID_IMyClient, &LIBID_MyATLComLib, /*wMajor =*/ 1, /*wMinor =*/ 0>,
public IDispEventSimpleImpl<SINK_ID, CMyClient, &MyServer::DIID_IMyEvents>
{
public:
typedef IDispEventSimpleImpl</*nID =*/ SINK_ID, CMyClient, &MyServer::DIID_IMyEvents> SomethingHappenedEvent;
...
BEGIN_SINK_MAP(CMyClient)
SINK_ENTRY_INFO(SINK_ID, MyServer::DIID_IMyEvents, 0x1, OnSomethingHappened, &SomethingHappenedInfo)
END_SINK_MAP()
...
private:
CComQIPtr<MyServer::IMyComServer> mMyComServer;
public:
STDMETHOD(InitHandler)(IUnknown* myserver);
STDMETHOD(ShutdownHandler)(void);
void __stdcall OnSomethingHappened(DateTime timestamp, string message);
};
一些生成的代码被保留为“...”
_ATL_FUNC_INFO SomethingHappenedInfo = { CC_STDCALL, VT_EMPTY, 2 , {VT_DECIMAL, VT_BSTR} };
STDMETHODIMP CMyClient::InitHandler(IUnknown* myserver)
{
this->mMyComServer = myserver;
SomethingHappenedEvent::DispEventAdvise((IDispatch*)this->mMyComServer);
return S_OK;
}
STDMETHODIMP CMyClient::ShutdownHandler(void)
{
SomethingHappenedEvent::DispEventUnadvise(this->mMyComServer);
return S_OK;
}
void __stdcall CMyClient::OnSomethingHappened(DateTime timestamp, string message)
{
...
}
请注意这里的 Advise/Unadvise 调用是不同的。
【讨论】：