Support retrieving multiple file contents on drop

[miloush]

Scenario:

User grabs multiple attachments in Outlook and drags & drops them into a WPF application. The application should be able to read the contents of all the files.

Current state:

The existing DataObject.GetData("FileContents") API only returns the first file. Other files need to be accessed by specifying the appropriate FORMATETC.lindex member, which is accessible through DataObject.OleConverter.GetData but not using the public API.

Proposed solution:

Add public GetData(string format, bool autoConvert, int index) overload to System.Windows.DataObject that would pass the index to the underlying DataObject.OleConverter.GetData or DataObject.DataStore.GetData method. Ideally, this would be added on the IDataObject interface but that would be a breaking change since it's public.

Note: This would enable developers to retrieve file content of all the dropped files. The developer would still need to obtain the file names and count by other means if needed, but reading the associated FileGroupDescriptor structure that is accessible through the existing API is much more straightforward then re-implementing the whole IDataObject API.

[JeremyKuhne]

@miloush I'll look at this as soon as I'm able.

[miloush]

Thanks @JeremyKuhne! I think in the private core assembly we only need the get/set data overloads with the index exposed (can default to -1), which would be great to do while we are introducing a new interface here. WinForms can benefit from it too.

The rest of the story we can manage on the WPF side.

[JeremyKuhne]

Thanks @JeremyKuhne! I think in the private core assembly we only need the get/set data overloads with the index exposed (can default to -1), which would be great to do while we are introducing a new interface here. WinForms can benefit from it too.

The rest of the story we can manage on the WPF side.

@miloush I'm going to be going through more "direct" scenarios that allow doing more manual "disassembly" of incoming data. I'll look at your specific proposal for dealing with this and consider if there might be other approaches. I'll circle back.