Set custom collections for previews

[DasicPhilipp]

I have an implementation of a TreeView, where I have an implementation of multiple selection. However, I cannot configure DragHandler to use my own collection instead of what the inhereted TreeView class offers. I found where the default DragDropPreview determines if it's a collection or not:

private static bool IsMultiSelection(IDragInfo dragInfo)
{
        return dragInfo?.Data is IEnumerable and not string;
}

But I don't see any opportunities to impact on dragInfo.Data. I tried to do it in DragOver() method in my DragHandler implementation:

void IDropTarget.DragOver(IDropInfo dropInfo)
{
        dropInfo.Data = SelectedItems;
        dropInfo.DragInfo.Data = SelectedItems;
}

But it seems like it's too late to set the data here, since it's been already rendered.

Is there any workarounds to achieve the desired behaviour or do we need to change something in the library?

As far as I see, the library relies at MultiSelector class. However, it's not possible to inherit from it since TreeView doesn't support it. My custom implementation still inherits from TreeView, so it seems like I need to fork the library to reinvent it or make a pull request.
https://github.com/punker76/gong-wpf-dragdrop/blob/develop/src/GongSolutions.WPF.DragDrop/Utilities/ItemsControlExtensions.cs#L60