Adding an in-proc COM Server object to a C# application

Question

I am new to COM and need to add a Server COM object to my c# application so I can call its methods and implement events. The documentation I have says this requires a COM-aware language such as Visual C++. My app is written in C# so I'm not sure how this is going to work. Any direction would be appreciated.

I am writing an app that communicates with a serial hypercom terminal. The device came with a DLL (the com server interface) that I will need to figure out how to use in my c# application.

I added a reference to the DLL to my project, which shows up as a type library. In object explorer I get interfaces, and some classes etc.

Thanks, Matt

Reed Copsey · Accepted Answer · 2010-08-07 00:00:42Z

1

You can add the COM object as a reference. .NET will create an interop assembly to work with the COM object, just like it was a .NET type.

answered Aug 7, 2010 at 0:00

Reed Copsey

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2 Comments

user404068 Over a year ago

Thanks, I added a reference to the DLL to my project, which shows up as a type library. In object explorer I get interfaces, and some classes etc. Now I just don't know how to use them really since the only sample code I have is in C++ and uses a class that inherits from CComObjectRoot.

Reed Copsey Over a year ago

@pkan522: You should have some objects you can instantiate in that library (which implement the interface(s) you need). Just construct them like any other .NET object.

Ismael · Accepted Answer · 2010-08-07 02:23:29Z

CComObjectRoot can be used as a base class for all COM objects implemented with ATL. As such you don't have to worry to implement something similar in C#, the required methods (AddRef, Release, QueryInterface) will be generated by tlbexp for classes that are tagged with ClassInterface.
STDMETHODIMP is a define which serves to declare the most common methods that can be called from COM (#define STDMETHODIMP HRESULT STDMETHODCALLTYPE). Again if your class is tagged with ClassInterface you will not have to worry about.
Such construction is required in C++ when your class implements several interfaces. I think this is not required if you tell C# compiler that your C# object implement IDispatch, IFPESOlementationEvents. The appropriate code will be written automatically by the compiler.

Probably everything will not make much sense if you are new to COM and C#, I'll suggest to take a look at the various introduction that you may find on the web, like this.

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