I made new document type in umbraco.then made some node by this document type in content. i will set up a new search index so found this code that Setting up a new search index.
@* Get the search term from query string *@
@{var searchTerm = Request.QueryString["search"];}
@{var results = ExamineManager.Instance.Search(searchTerm, true); }
but i do not know how to limited this code that can search only in my document type.