I am running through the LINQ examples on the Microsoft site and I am
wondering where the List object below is coming from?  What classes do I
need to add to my page to be able to use this List object?

public void Linq3() {
   List products = GetProductList();

   var expensiveInStockProducts =
       from p in products
       where p.UnitsInStock > 0 && p.UnitPrice > 3.00M
       select p;
   
   Console.WriteLine("In-stock products that cost more than 3.00:");
   foreach (var product in expensiveInStockProducts) {
       Console.WriteLine("{0} is in stock and costs more than 3.00.",
product.ProductName);
   }
}