c# - Why I get error: are you missing a using directive or an assembly reference? -

i added c# code in aspx file, showing error.

this code add asp file:

   [system.web.services.webmethodattribute, system.web.script.services.scriptmethodattribute]    public static string[] getcompletionlist(string prefixtext, int count)    {         string[] names = {"ram","ankit","sam","sahil","rajan","rahul","sajan"};         var nameslist = tmp in names tmp.tolower().startwith(prefixtext) select tmp;      return names;     } 

i error:

compiler error message: cs1061: 'string' not contain definition 'startwith' , no extension method 'startwith' accepting first argument of type 'string' found (are missing using directive or assembly reference?) 

here n declared in page:

<%@ import namespace="system" %> <%@ import namespace="system.io" %> <%@ import namespace="system.collections" %> <%@ import namespace="system.collections.specialized" %> <%@ import namespace="system.runtime.serialization" %> <%@ import namespace="system.text" %> 

any idea how can fix error?

you forgot s in startswith - startwith.