Hello,
I have a VB ASP website that I am converting to .NET and c#. The old site used a DLL file to perfom some DB calculations. I am trying to work with the COM DLL from an MFC application.
In the ASP page a function of the DLL is called as follows:
Set objTerminator = Server.CreateObject("Proje
str = objTerminator.returnCharty
Set objTerminator = Nothing
Terminator = str
I am trying to call it from MFC as follows:
CgetbyMemberId myWrapper;
COleException* pe = new COleException;
try
{
if (myWrapper.CreateDispatch(
{
CString csMemberGuid = _T("9C5B442E46B0F361F1416F
int nChartType = myWrapper.returnChartype(c
CString csChartType;
csChartType.Format(_T("Val
m_ChartTypeStaticText.SetW
}
else
{
throw pe;
}
}
catch (COleDispatchException* pe)
.
.
.
But, I fail in the following place in the DLL:
long myErrReturn = (long)1;
IObjectContext* pObjectContext = NULL;
MTS_message_flag_one = TRUE;
error_message_flag_five = TRUE;
HRESULT hr = S_OK;
pass_error_all = 0;
try{
if(MTS_message_flag_one == TRUE)
{
hr = GetObjectContext(&pObjectC
if (!SUCCEEDED(hr))
{
pObjectContext->SetAbort()
*error_return = (long)pass_error_all;
return *error_return;
}
}
The above fails because pObjectContext is null.
I am unfamiliar with IObjectContext and do not do much VB programming. So my question is how can I get this DLL to work from MFC? Where does thos IObjectContext come from? Is it something the webserver creates?
Any help would be greatly appreciated. I am at a loss and hope this all makes sense.
Oh, also, ultimately, I will want to call this DLL from .NET/C#.
Thanks,
Tony
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The documentation of this method says that:
The method can return a NULL context in following cases:
CONTEXT_E_NOCONTEXT
The current object doesn't have a context associated with it because either the component wasn't imported into an application or the object wasn't created with one of the COM+ CreateInstance methods.
Yes, I read that also, however, I am using MFC and it creates a COM wrapper. When you looked at how I was calling the function in the DLL (from my code above) I am using CreateDispatch.
I must have context associated with it because the LIVE DLL expects it. If it cannot get the Context Object the pointer is null and the DLL crashes. I do not have source to the DLL to change that right now.
Are you saying that if I use CoCreateInstance and QueryInterface I would have the context?
if that is true, can you help with some sample code. Again, i am unfamilar with IObjectContext and have not used CoCreateInstance and QueryInterface in a long time.
Thanks,
Tony
ASP runs inside a COM+ activity context. An activity context defines the boundary for transaction processing (in a database sense).
All ASP pages have a context. And if not specified they get a default context.
Your MFC application is attempting to invoke a COM+ component outside of any activity context, hence it gets the CONTEXT_E_NOCONTEXT error.
Assuming that your MFC application runs standalone (runs by itself and not part of, say, a web page), you will need to manually create an outermost activation context for the COM+ component.
In your MFC app create the COM+ activation context by calling CoCreateActivity. This will return an interface pointer to an IServiceActivity. You need to define a COM object that implements IServiceCall and pass it to IServiceActivity::Synchron
For a starting point see http://msdn.microsoft.com/
Another simpler method is to use the newer APIs CoEnterServiceDomain and CoLeaveServiceDomain. http://msdn.microsoft.com/
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Answer for Membership
by: sumitkchawlaPosted on 2009-02-26 at 02:11:39ID: 23743087
Use CoCreateInstance to create an object of your Class, and then use QueryInterface to find the Interface pointer.
http://netez.com/2xExplore