/// <summary>
/// Method called when dropping an item.
/// </summary>
/// <param name="dropInfo"></param>
async void IDropTarget.Drop(IDropInfo dropInfo)
{
// Get source and target
TodoViewModel sourceItem = dropInfo.Data as TodoViewModel;
TodoViewModel targetItem = dropInfo.TargetItem as TodoViewModel;
// Let the Todo-items switch places
Todos.Move(Todos.IndexOf(sourceItem), Todos.IndexOf(targetItem));
// Update todo order
await UpdateTodoOrder();
DragHandleActive = false;
}