How to exclude contentlink id in search result

Hi guys, 

I have a problem when a customer search a product code(Article number) e.g. 1512 in Find.

It included a product which have ContentLink ID 1512 (product code 70405) in search result.

How can I exclude the contentlink id in the search result?

I have the following code:

multiSearch = searchClient.Search<ContentData>()
.For(query)
.FilterByExactTypes(new[] { typeof(Article), typeof(Category), typeof(StandardPage) })
.FilterForVisitor(currentLanguage)
.FilterMarket(new IMarket[] {currentMarket})
.Skip(skip).Take(itemsPerPage).Track().GetContentResult();

Thanks, 

ChiChing