I'm trying to implement a Windows Autoplay handler; according to the documentation and the examples I found, I'm supposed to query the IDataObject
for the "Autoplay Enumerated IDList Array"
clipboard format.
So I tried to do something like that:
[DllImport("user32.dll", SetLastError = true, EntryPoint = "RegisterClipboardFormatW")]
public static extern uint RegisterClipboardFormat([MarshalAs(UnmanagedType.LPWStr)] String format);
private const string CFSTR_AUTOPLAY_SHELLIDLISTS = "Autoplay Enumerated IDList Array";
private static readonly uint AUTOPLAY_SHELLIDLISTS = RegisterClipboardFormat(CFSTR_AUTOPLAY_SHELLIDLISTS);
...
public int Drop(IDataObject pDataObj, int grfKeyState, Point pt, ref DropEffect pdwEffect)
{
var fmt = new FORMATETC
{
cfFormat = (short)AUTOPLAY_SHELLIDLISTS,
ptd = IntPtr.Zero,
dwAspect = DVASPECT.DVASPECT_CONTENT,
lindex = -1,
tymed = TYMED.TYMED_HGLOBAL
};
int hr = pDataObj.QueryGetData(ref fmt);
if (hr == S_OK)
{
...
}
return 0;
}
But QueryGetData
always returns S_FALSE
(and GetData
throws, obviously). So I tried to enumerate the available formats with EnumFormatEtc
:
it returns only one format
it returns 4 formats, none of which is the same as the one I passed to QueryGetData
( cfFormat
values are -16238, 15, -16378 and -16377). If I use the first format from EnumFormatEtc
, instead of AUTOPLAY_SHELLIDLISTS
, everything works fine, but I don't think it's the right way to do it...
Could someone explain what is going on? Am I using the wrong format?
EDIT: apparently the first format returned from EnumFormatEtc
is "Shell IDList Array"
; clearly I can work with that, but what happened to "Autoplay Enumerated IDList Array"
?
OK, I finally found a much easier way to do it, using the System.Windows.Forms.DataObject
class:
public int Drop(IDataObject pDataObj, int grfKeyState, Point pt, ref DropEffect pdwEffect)
{
try
{
var dataObj = new DataObject(pDataObj);
if (dataObj.ContainsFileDropList())
{
StringCollection files = dataObj.GetFileDropList();
// Do something with files...
}
return 0;
}
catch(Exception ex)
{
Trace.WriteLine(string.Format("Error: {0}", ex));
return 1;
}
}
No need for any low-level COM interop (except the IDropTarget
interface declaration)...
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