adding dynamic id to Ajax commandLink

[Jignesh Patel]

I have following code

a:commandLink id="#{_subCategory.subCatId.toString()}" value="#{_subCategory.subCatNm}" action="#{postAdAction.displayAdScreen(_subCategory.subCatId)}"/>  

However, it says illegal argument exception for id. Now _subCategory.subCatId is of type short and I have converted it to String. Any insight why there is a still problem?
Moreover if I have to create id like

"#{link+_subCategory.subCatId.toString()}"

is there any way to do that?