C# 4 and .NET 4

Using a CoM Component from a .neT Client ❘ 705
};
[id(1)] HRESULT Add([in] LONG val1, [in] LONG val2,
[out, retval] LONG* result);
[id(2)] HRESULT Sub([in] LONG val1, [in] LONG val2,
[out, retval] LONG* result);
The coclass COMDemo must also be changed so that it implements both the interfaces IWelcome and
Math. The IWelcome interface is the default interface:
importlib("stdole2.tlb");
[
uuid(ACB04E72-EB08-4D4A-91D3-34A5DB55D4B4),
helpstring("COMDemo Class"),
custom(0F21F359-AB84-41e8-9A78-36D110E6D2F9,
"Wrox.ProCSharp.Interop.Server.COMDemo")
]
coclass COMDemo
{
[default] interface IWelcome;
interface IMath;
};
Now, you can set the focus away from the IDL file toward the C++ code. In the file COMDemo.h, you can find
the class definition of the COM object. The class CCOMDemo uses multiple inheritances to derive from the
template classes CComObjectRootEx, CComCoClass, and IDisplatchImpl. The CComObjectRootEx class
offers an implementation of the IUnknown interface functionality such as implementation of the AddRef()
and Release() methods. The CComCoClass class creates a factory that instantiates objects of the template
argument, which here is CComDemo. IDispatchImpl offers an implementation of the methods from the
IDispatch interface.
With the macros that are surrounded by BEGIN_COM_MAP and END_COM_MAP, a map is created to define all
the COM interfaces that are implemented by the COM class. This map is used by the implementation of the
QueryInterface method.
class ATL_NO_VTABLE CCOMDemo:
public CComObjectRootEx,
public CComCoClass,
public IDispatchImpl
{
public:
CCOMDemo()
{
}
DECLARE_REGISTRY_RESOURCEID(IDR_COMDEMO)
BEGIN_COM_MAP(CCOMDemo)
COM_INTERFACE_ENTRY(IWelcome)
COM_INTERFACE_ENTRY(IDispatch)
END_COM_MAP()
DECLARE_PROTECT_FINAL_CONSTRUCT()
HRESULT FinalConstruct()
{
return S_OK;
}
void FinalRelease()
{
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