How do I search an ActiveX/COM object for a method? - dll

Question

I have an ActiveX/COM DLL. It contains many methods and properties. I would like to be able to ask it if it has a particular symbol, as per the following snippet:
If HasMethod( "StdLib.DLL", "ReadFileE" ) Then
...
End If
Is there a way to do this from, say, VBScript or JScript? If not, where do I go to get the information I need?

Answer 1

After Googling around not quite finding what I wanted, I remembered the Edanmo site which got me thinking about TLBINF32.DLL, downloading Microsoft's TLBINF32.CHM and reading up on GetMembersWithSubStringEx. Below is the implementation of it (done in VB6 with a reference to TLBINF32.DLL), some demo VBScript and output, and the wrapping of that functionality in some VBA.
Public Function SearchTLIMethodsAndProperties(sTypelib As Variant, sSymbol As Variant) As Variant
Dim SI As SearchItem
Dim aResults As Variant
Dim bFound as boolean
Dim Groups(1) As InvokeKinds
Groups(0) = INVOKE_FUNC Or INVOKE_PROPERTYGET Or _
INVOKE_PROPERTYPUT Or INVOKE_PROPERTYPUTREF
ReDim aResults(0)
bFound = False
With TypeLibInfoFromFile(sTypelib)
.SearchDefault = tliStClasses Or tliStEvents
For Each SI In .GetMembersWithSubStringEx(sSymbol, Groups)
bFound = True
arr.AAdd_PostIncrement aResults, SI.Name
Next
End With
if bFound then
ReDim Preserve aResults(UBound(aResults) - 1)
end if
SearchTLIMethodsAndProperties = aResults
End Function
VBScript demo. The above code was included in my StdLib DLL in the Registry coclass.
Dim O, R
Set O = CreateObject("Std.Registry")
Set R = CreateObject("Std.Arrays")
WScript.Echo R.ShowStructure( O.SearchTLIMethodsAndProperties( "MSSCRIPT.OCX",""))
Output from the demo (script was run in SciTE).
>cscript "C:\foo\foo.vbs"
{Add,AddCode,AddObject,AllowUI,Clear,CodeObject,Column,Count,Description,Error,Eval,ExecuteStatement,HasReturnValue,HelpContext,HelpFile,Item,Language,Line,Modules,Name,NumArgs,Number,Procedures,Reset,Run,SitehWnd,Source,State,Text,Timeout,UseSafeSubset}
>Exit code: 0
Finally, the VBA code. A cell has a symbol in it and this routine finds it or returns an error string.
Public Function LookupSymbol(sSym As String) As String
Dim aRes As Variant
aRes = reg.SearchTLIMethodsAndProperties("MSSCRIPT.OCX", sSym)
Dim i As Integer
LookupSymbol = "!!NotFound!!"
For i = 0 To UBound(aRes)
If LCase$(aRes(i)) = LCase$(sSym) Then
LookupSymbol = sSym
Exit For
End If
Next
End Function
Looking back on it now, I think I might pass in the path to the DLL/OCX as the first parameter.

Answer 2

I have used Microsofts interactive OLE/COM-Object viewer to find mehods and their parameters in ActiveX-DLLs. Maybe looking at the source code of the viewer will lead you in the right direction: MSDN OleView sample

Answer 3

If you want to do it programmatically - I'm not aware of a simple way to do that. Anyway, if you really need to (and if your programming language is capable enough) - you can query the type library (refer to ITypeLib description somewhere at http://msdn.microsoft.com/en-us/library/ms221549.aspx).
Also, if you already have an IDispatch pointer - you might consider using its services to dynamically enumerate methods supported by the interface (refer to IDispatch description in MSDN).