How do I check if a COM dll is registered in C#

I created a Office Add-In in VS 2008, C#, .NET 3.5, and VSTO. It is deployed via ClickOnce. A run-time configuration form executes regsvr32 to register "fooapi.dll" included with the project that can not be registered during instal du开发者_Python百科e to ClickOnce limitations. Is there any prefered way to check and see if "fooapi.dll" is registered during run-time in C#?

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Try the Type.GetTypeFromCLSID or Type.GetTypeFromProgID methods to quickly check for a COM interface's existence.

Alternatively, just instantiate the object and trap the exception, e.g.

catch(COMException ex) {
    if(ex.ErrorCode == -2147221164) {
        // Retrieving the COM class factory for component with CLSID XXXX failed
    }
}

UPDATE:

This overload appears to be the only one that actually returns null if the COM object cannot be instantiated.

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If you know the DLLs GUID, you could check the existance of the registry key in HKCU\SOFTWARE\Classes.

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Check the presence of HKEY_CLASSES_ROOT\CLSID\{your_CLSID} and the proper values under it. You could probably get away with looking for InprocServer32 and Codebase values only, but you might also opt-in for more extensive check.

You can also just create an instance of the component. However, if both the component and the client are C# and you use new, the CLR might be able to figure out the proper assembly and load it with going through COM. (Yes, it can be smart like that sometimes :-)). You should explicitly p/invoke to CoCreateInstance

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If you have the progID of the component in the DLL, you can try getting the Type:

System.Type.GetTypeFromProgID(string progID, bool throwOnError)

If you get System.Runtime.InteropServices.COMException, it means that the progID is not registered.

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I think the simplest way is to try and create the component which lives in fooapi.dll. Wrap the creation code in a try/catch block and catch the exception which is generated if the DLL is not properly registered. This is the surest way to check for correct registration