EnumerateResourcesActivity

I am initializing eumerateresourcesactivity from a function :-

 eumerateresourcesactivity .ActorId=new Guid(FIMAdminGuid);
 eumerateresourcesactivity .XPathFilter="/Person[AccountName='" + accountName + "']");//accountname is a variable.
My enumerateResourcesActivity is getting triggered but not returning any results even though account is present in FIM.
Can anybody let me know where I am going wrong.