Importing ActiveX Controls
There
are a lot of articles in net for using standard COM components in .NET
applications. This article is about importing a particular kind of COM
component, a graphical one: the ActiveX control. I�ve tried to import the MSMAPI
ActiveX library. Before importing here is a brief introduction to ActiveX and
MAPI.
What
is an ActiveX control? An ActiveX control is really just another term for �OLE
Object� or, more specifically �COM Object�. In another words, it supports
IUnknown interface and is also self-registering. With the help of
QueryInterface, a container can manage the lifetime of the control, as well as
dynamically discover the full extent of a control�s functionality based on the
available interfaces. This allows a control to implement as little
functionality as it needs to.
MAPI
is the Messaging Application Programming Interface, represents a comprehensive
set of specifications that link messaging applications on the one hand and the
service providers on the other, forming a messaging architecture. Although
Microsoft is the prime supplier of MAPI components, it is by no means necessary
to have a single Microsoft component to use MAPI (nor it is
necessary to use a Windows or Win32 platform, actually). We can have a MAPI-complaint
system with third party message store, address guide, and transport providers
on a non-Windows operating system. MAPI is a part of WOSA, the Windows Open
Services Architecture, which consists of common set of APIs for distributed
computing. For more details, read MSDN.
Now, lets see how to import an ActiveX control. There are
two ways to use ActiveX controls under .NET. We have an application called
AxImp.exe, shipped with .NET SDK. This application does a similar kind of
service for ActiveX controls that TlbImp.exe performs for non-graphical COM
components. Basically, what it does is, it generates a wrapper component
containing a type library that .NET can understand, and this wrapper component
is capable of marshalling calls between the .NET runtime and the underlying COM
object (the control). This application can from the command line, simply by
passing the path and filename of the control.
This will
create the file as <old_file.ocx> to <old_file.dll> and
Ax<old_file.dll>. After creating the wrapper component add a reference to
it and start using the control.
The
other way is to import directly to the Visual Studio. We can add the controls
to the toolbox by simply right clicking one of the tabs and selecting Customize
Toolbox from the context menu. To do this select the COM Components tab and
select or browse for the controls, you want to add. Here we want MAPI messages
control and session control.
By
doing this, we enable the Visual Studio, to create the wrapper component. After
this we can use the wrapper component as proxy library, just like any other
.NET component. Here is an example, to use this component to log on to MAPI
session and send e-mail.
MAPISession objSession = new MAPISession();
MAPIMessages objMsg = new MAPIMessages();
objSession.SignOn();
objMsg.SessionID = objSession.SessionID;
objMsg.Compose();
objMsg.MsgSubject = "MAPI TEST";
objMsg.MsgNoteText = "The message body";
objMsg.RecipAddress = "mailto:mercy_gp@dell.com">mercy_gp@dell.com";
objMsg.ResolveName();
objMsg.Send(null);
objSession.SignOff();
That�s all.
