asp.net mvc 4 - Autocomplete or create new object for model -

i'm trying implement similar so/gmail tag system: "try find matching tag or create new".

i have 2 simple classes:

public class item {     [key]     public int itemid { get; set; }     [required]     public string name { get; set; }     public int categoryid { get; set; }     public virtual category tag { get; set; } }  public class category {     [key]     public int categoryid { get; set; }     public string name { get; set; } } 

the categorycontroller implements autocompletecategory-method returns json list of available categories:

public jsonresult autocompletecategory(string term) {     var result = categoryrepository.all.where(category=> category.name.tolower().contains(term.tolower())).distinct();      return json(result, jsonrequestbehavior.allowget); } 

i have jquery-script sends request method , displays matches.

now problem:

what need use in _createoredit-view map edit-field model? represent category, bind categoryid, simple key, don't i?

and if edit field contains unknown category, how can create , bind model?