How to match data fields from text files

There are a huge number of ways to do this: but assuming that the two files are not necessarily in the same order, I would create a class which contained the Price and Description (call it "Item" maybe) then create a Dictionary of Items:

private Dictionary<int, Item> items = new Dictionary<int, Item>();

I would then read each file in turn, breaking it into itemcode and either Price or Description and do this with each row:

if (!items.ContainsKey(itemcode))
   {
   items.Add(itemcode, new Item());
   }
//items[itemCode].Price = price;
//items[itemCode].Description = description;

uncommenting the appropriate line.
At the end, you have a Dictionary which contains each Item, hopefully complete with each Price and Description.

It's a poor way to store your data though!