Using ActiveX In a windows service

[Big Trev]

I have an app which uses an ActiveX component. No problmes there. I have now converted it to run as a windows service, which also work fine when i configure the service to run using my NT Login account. However, when i configure the service to run using the System Account, i get an exception: System.IO.FileNotFoundException: The specified module could not be found. when the code tried to instantiate the ActiveX control. I have the Path to the Dll in the system environment. Does any one have any ideas? Thanks

[Heath Stewart]

With ActiveX, the PATH environment variable doesn't really matter (it can, but is not typically necessary, because...). When an ActiveX control is registered, it's server's path (the executable that contains the control) is registered in the Windows registry under HKEY_CLASS_ROOT\CLSID. This is one thing that makes COM so attractive - you don't have to worry about where the file is (thus helping to eliminate DLL hell, so long as you follow good COM guidelines about interface naming and the like). Make sure the ActiveX DLL (or OCX or whatever) is registered correctly using regsvr32.exe. The other possibility is that the interop assembly was not found. When you import an ActiveX control (or even a typelib) interop assemblies are generated, which are also called Runtime Callable Wrappers, or RCWs. Those assemblies must be either in the same directory as the service executable, in the probing path (configurable in the .config file, which must also be in the same directory as the service executable and named the same as the executable + ".config"), using the <assemblyBinding> section in your .config file, or installed into the Global Assembly Cache (GAC), which requires that the assembly be signed (it's easy, just use sn.exe -k KeyFile.snk to generate a key pair).

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