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Visual Studio110
Hi all,

here I am again :-( , this turn I'm in trouble with

IShellFolder.GetUIObjectsOf, which raise an exception while accessing an

uninstantiated object (I have Italian version softwares and I litteraly

translate the error, the original error may sound a little different).



I'm using VB.Net, and I need to access ThumbImage extractor, I got

IShellFolder interface object pointing to the Directory where my file is in

(in following code it's named item), I know it' Ok since I can enumerate

contained objects through EnumObjects. Also Pidl is okay since

PathFromPidl(pidl) return a correct value. IntPtr.Zero, 1 and prgf should be

okay too :-).

So the problem seems to be IUnknown but shouldn't it be an output parameter?

Or It may be interface definition...



(by the way: how to instantiate a com object like IUnknown interface ?)



This is the code



Dim pidlPath As String = PathFromPidl(pidl)



' pidl is a relative pidl, so only the filename portion is relevant

If Path.GetFileName(pidlPath).Equals(Path.GetFileName(file)) Then

ret = True



Dim iUnk As IUnknown

' Try and get the IExtractImage interface:

Dim prgf As UInt32

Dim iidExtractImage As Guid = New

Guid("BB2E617C-0920-11d1-9A0B-00C04FC2D6C1")

item.GetUIObjectOf(IntPtr.Zero, 1, pidl, iidExtractImage, prgf,

iUnk)



'some code

End If



Here is the interface (just the method)



<PreserveSig()>_

Function GetUIObjectOf(ByVal hwndOwner As IntPtr,

<MarshalAs(UnmanagedType.U8)>ByVal cidl As Long, ByRef apidl As IntPtr,

ByVal riid As Guid, ByRef rgfReserved As UInt32, ByRef ppv As IUnknown) As

Int32



What's wrong?



Thanks, Nicola


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Nicola,



cidl should be an Integer. riid should be passed ByRef.







Mattias



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Mattias Sjögren [MVP] mattias @ mvps.org

www.msjogren.net/dotnet/">www.msjogren.net/dotnet/ | www.dotnetinterop.com">www.dotnetinterop.com

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