问题描述
可以将使用C#编写的托管事件公开并使用在使用c ++编写的COM对象中。不熟悉com和atl。你能否显示MSDN文章中显示的示例的C ++方面的内容。
It is possible to exposed managed events written in C# to be exposed and used in a COM object written using c++. not being that familiar with com and atl. Can you please show what would the C++ side of things would look like for the example shown in the MSDN article
显示的VB6代码证明它是可行的。
The VB6 code shown proves that it is doable.
提前感谢
推荐答案
在C ++中最简单的方法是,IMO将通过ATL的 IDispEventImpl
和的帮助来实现一个事件接收器IDispEventSimpleImpl
模板。示例项目。
The easiest way in C++ would be, IMO, to implement an event sink with help of ATL's IDispEventImpl
and IDispEventSimpleImpl
templates. An explanation with sample project can be found here.
有很多关于如何做到这一点的在线资源,例如或,但以下是所需步骤的列表:
There are many online resources about how to do this, e.g. this or this, but here is the list of required steps:
首先让我们来看看管理端。
First let's take a look at managed side.
为了提供事件,我们必须执行以下操作:
In order to provide events, we must do the following:
- 声明一个事件接口(
IDispatch
- 基于) - 在coclass $中实现匹配事件b $ b
ComSourceInterfaces 属性将coclass标记为将事件接口绑定到coclass
- declare an event interface (
IDispatch
-based) - mark the coclass with
ComSourceInterfaces
attribute to bind the event interface to coclass - implement matching events in the 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,但是您可以尝试MFC或手动进行。
Now, back to unmanaged side. I will use ATL, as I find it the most effective way to write COM clients, but you can try MFC or do it 'manually'.
需要执行以下步骤:
- 接收器将继承
IDispEventSimpleImpl
(或IDispEventImpl
) - 所有需要的方法的汇图都被声明为
- 处理方法为每个事件编写
- 接收器最终注册了事件源
- ,当不再需要时,接收器断开连接
- the sink will inherit
IDispEventSimpleImpl
(orIDispEventImpl
) - sink map with all the needed methods is declared
- handler methods are written for each event
- the sink is registered with event source
- eventually, when not needed anymore, the sink is disconnected
这是ATL C ++客户端中的代码:
Here's the code in an ATL C++ client:
// 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 someEvent
Now, we need to define the type info members in the cpp file (i.e. the
someEvent
instance from example above):
_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 -----------------------------------------+
这可能很棘手,因为类型映射并不总是很明显(例如,它可能很清楚管理
int
映射到 VT_I4
,但不太明显的是 DateTime
映射到 VT_DECIMAL
)。
您需要声明您计划在汇图中使用的每个事件 - 如果您不需要它们,则不要映射它们。
This can be tricky as type mappings are not always obvious (e.g. a it might be clear that managed
int
maps to VT_I4
, but it is less obvious that DateTime
maps to VT_DECIMAL
).You need to declare each event you plan to use in the sink map - if you don't need all of them, don't map them.
现在,您需要将您的接收器连接到事件源:
Now you need to connect your sink to the event source:
// 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);
这是它,或多或少。使用
IDispEventImpl
而不是 IDispEventSimpleImpl
导致少一些代码,因为您不需要提供类型信息对象这可能是最丑的部分。然而,它有两个缺点:
This is it, more or less. Using
IDispEventImpl
instead of IDispEventSimpleImpl
results in a bit less code, as you don't need to supply the type info objects which might be the ugliest part. However, it has two drawbacks:
- 需要访问typelib(因为它需要读取界面元数据才能提供类型信息本身)
- 有点慢(但我猜不会显着)
这篇关于使用C ++将管理事件暴露给COM的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!