Dragging a directory into the filetree breaks drag and drop

[wldevries]

When you drag a directory into the file tree nothing happens and any subsequent drag operation fails.

The problem is that the method MainWindow.CreateDirectoryPromptAsync is called from a non-UI thread which breaks the operation. This is because in FileTree.Tree_Drop the add file or directory operations is run on a spawned task instead of on the UI thread.

[BenLubar]

MainWindow.CreateDirectoryPromptAsync should be fine to call from any thread since it uses the dispatcher for its UI calls:

UniversalPackageExplorer/UniversalPackageExplorer/MainWindow.Content.cs

Lines 390 to 404 in 46351ed

	name = await this.Dispatcher.InvokeAsync(() =>
	{
	var prompt = new NamePromptWindow("Folder Name Conflict", "New folder name:", NamePromptWindow.CreateNameValidator(true, collection, collection == this.Package.Metadata, prefix))
	{
	Text = name,
	Owner = this
	};
	if (prompt.ShowDialog() == true)
	{
	return prompt.Text;
	}
	return null;
	});

[wldevries]

It could be my analysis is flawed, but the behavior is as described