Full outer join linq using union

I have two lists

var left={[ID=1,Name='A',Qty1=0,Qty2=5],[ID=2,Name=B,Qty1=0,Qty2=52]};
var right={[ID=1,Name='A',Qty1=57,Qty2=0],[ID=2,Name=B,Qty1=84,Qty2=0]};
var outer=left.union(right);

I want to get the following result:

outer={[ID=1,Name='A',Qty1=57,Qty2=5],[ID=2,Name=B,Qty1=84,Qty2=52]}

How do I get that? How to write the comparator class?

Edit: I have two lists

var target=(...new ClassA{ID=a.ID,Name=a.Name,TargetQty=b.TargetValue}).ToList();
var sales=(....new ClassA{ID=a.ID,Name=a.Name,SalesQty=b.SaleValue}).ToList();

Now I want a full outer join. How can I get that?