Alright, I am not by any means an expert C++ programmer, so please bare with me.
I have created a com object that will be implemented within C#, the reason for this com object is to create a persistent object of another library. My situation is this. I have the complete com object created, but would like to add additional supporting features, i.e.:
An object that is defined within the C++ com object, such as a struct containing an int, a wchar_t*, and a boolean value. I would like to be able to utilize the object type from within C# to store the object rather than have a new object type in C#. I have seen this done in many cases, but just have no clue where to find such direction for supporting this.
I would also like the come object (Item)'s methods of:
typedef struct MyItemType
{
int myItn;
wchar_t* myChar;
BOOL myBool;
};
[propget, id(1)] HRESULT Item([out, retval] MyItemType* pVal)
STDMETHOD(get_Item)(MyItemType* pVal);
to be able to be implemented. As it stands right now, I have created a struct with in the header file of my C++ com object, and am using this. But i get the following error.
Error 1 error MIDL2025 : syntax error : expecting a type specification near "MyItemType"
COM/ATL App Method Return/Pass defined types
Ravi Santha
Thank you for your reply, I apologize I guess I wasn't quite clear enough. I am trying to create the com object in C++ and call/use it from with in C#.
You state to place the struct inside the IDL, where woudl this be specifically, inside the class the interface the...
Also, I am aware that COM is dead, however, what would another method be I am open to suggestions.
Tryst
I don't remember this staff well(remember COM is dead:)) and defiantly have no idea if c# can do it, but I would do the following:
1. define struct inside of IDL
2. Define method of the object ([propget, id(1)] HRESULT Item([out, retval] MyItemType** pVal))
3. export the tlb into C# and implement the interface (very iffy with struct and such)
4. rest is easy if you #import from you cpp it will generate ready to use header files.
It might be easier if you had to use c++ com object from c#
Vladimir Chtepa
"struct [MIDL]" -
http://msdn2.microsoft.com/en-us/library/aa367271.aspx
article in MSDN describes it nicely)
the second way is mixed mode code where __gc class XXX wraps native unmanaged counterpart as a member, creating wrapper around unmanged code something like
public __gc class WrapperClassForDotNet : public IDisposable
{
public:
WrapperClassForDotNet(){m_old = new MyOldCPPClassIWantToReuse();}
void Dispose()
{
Dispose(true);
GC::SuppressFinalize(this);
}
__property int get_SampleValAsProperty()
{
if(!m_old)
return 0;
return static_cast<int>(m_old->SampleVal());
}
protected:
virtual void Dispose(bool disposing)
{
if(m_old)
{
delete m_old;
m_old = 0;
}
}
private:
MyOldCPPClassIWantToReuse* m_old;
};
We tried the second way in our App. It is incredibly difficult to debug and troubleshoot, but it seems to work