• Create a prg file for the interface
  

begin namespace COMTest

using System.Runtime.InteropServices

[ComVisible(true)];
[Guid("750E557E-9DA6-4508-A36E-C4141D27B5D4")];
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)];
interface ICOMTester
	
[DispId(1)];
method Output() as string
	
end interface          

end namespace

The GUID needs to be created with the GuidGen.exe tool.

• Create a prg file for the functionality itself:
  

using System.Runtime.InteropServices

begin namespace COMTest

[ComVisible(true)];
[Guid("7D1DF22E-3A3D-431C-8BEE-A2F40C53A249")];
[ClassInterface(ClassInterfaceType.None)];
[ProgId("COMTest.COMTester")];
class COMTester implements ICOMTester
	
public constructor()
	
	return
	
public virtual method Output() as string
	
	return "Hi from my component"
	
end class	

end namespace

• Build the application (i.e. the DLL)
  
• create a snk file: sn - k COMTest.snk
  
• add this snk file as signature to your DLL (Application Properties - Advanced - Assembly signing in XIDE)
  
• build your application
  
• read the public key from the application: sn -T COMTest.dll (upper case “T”) and write it somewhere
  
• create the TLB with administrative (elevated) rights: tlbexp COMTest.dll
• create the automation server in VO using the created TLB
• edit the Init() method of the created VO class adding the cProgId and the cClsId using the GUIDs from your library. The cClsId uses the GUID from your class, the cIID the one from your interface.

METHOD Init(ObjID, fROTCHECK) CLASS ICOMTester

self:cProgID := "COMTest.COMTester"
self:cClsID := "{7D1DF22E-3A3D-431C-8BEE-A2F40C53A249}" 
self:cIID := "{750E557E-9DA6-4508-A36E-C4141D27B5D4}"
SUPER:Init(ObjID, 0, .T., fRotCheck)
SELF:_dwFuncs := 1
SELF:_dwVars := 0

RETURN SELF

Possible problems:

• you can encounter error 0x80131044 when trying to create the TLB from a already strong named DLL if the dependencies of your COM dll are not strong named. In this case simply compile your library without the signing option
• you should set the namespace also in the project properties
• the exported class cannot have the same name as the COM DLL itself