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Exposing .NET Components to COM


Namespace: System.Runtime.CompilerServices

Building .NET Components for use by COM
.Net framework generates COM Proxies known as COM Callable Wrapper (CCW) to be used by COM. No matter how many COM clients consume a given managed object, .Net runtime will create a single CCW.

Write down you class and before building it, Select the configuration form the project properties named “Register for COM interop”.

Hiding public .NET Classes from COM
To hide a class or member just use the following attribute: [ComVisible(true/false)].

Deploying COM-Enabled Assemblies:
      Check the following necessaries before creating CCW:
1.       All class have default constructor (no parameter).
2.       Exposed Types should be public.
3.       Any member exposed should be public.
4.       Abstract classes will not be able to be consumed.

After this verification you can create CCW using Visual Studio or using tlbExp.exe.

Compile the type using VS 2005 or the following Command-line
            Csc /t:library ComVisibleObjectCollection.cs

Create a resource script file named: ComVisibleObjectCollection.res having text:
            IDR_TYPELIB1 typelib “ComVisibleObjectCollection.tlb”

Now, to create a resource file compile the resource script using the command:
            rc ComVisibleObjectCollection.res

And now compile the assembly and embed the resource as win32 resource:
Csc /t:library ComVisibleObjectCollection /win32res:ComVisibleObjectCollection.res
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