Flatten Tree to Array

ITree is a partial class for EF that just has Parent and Children props on it

private List FlattenTree(List items,List outputItems) where T:ITree
{

 foreach(var item in items){
 
 outputItems.Add(item);
 
 if(item.Children.Count > 0){
  return FlattenTree(item.Children, outputItems);
 }
 
 }

 return outputItems;
}