Use invoke code by sending dt1 as in/put and dt2 as in
dt1.AsEnumerable.Where(function(x) String.IsNullOrEmpty(x("Price").ToString.Trim)).ToList.ForEach(sub(r) r("Price") = dt2.AsEnumerable.Where(function(x) x("Name").ToString.Equals(r("Name").ToString AndAlso x("Product").ToString.Equals(r("Product").ToString)).First(function(x) x("Price").ToString))
Cheers