c# - Error with binding my cascading dropdownlist -

i facing error message when move page in c# application page contain cascading dropdownlist. didnt know how can fix please me it.

the parameterized query '(@country nvarchar(4000))select state state country =' expects parameter '@country', not supplied.

protected void page_load(object sender, eventargs e)     {         httpcookie cookie = request.cookies.get("location");           if (!ispostback)         {              if (cookie != null)             {                 datatable statedt = new datatable();                 using (sqlconnection con2 = new sqlconnection(configurationmanager.connectionstrings["beravaconnectionstring"].connectionstring))                 {                     // create selectcommand.                     sqlcommand command = new sqlcommand("select state state country = @country", con2);                      command.parameters.addwithvalue("@country", (cookie["location"]));                      sqldataadapter adaptar = new sqldataadapter();                     adaptar.selectcommand = command;                     adaptar.fill(statedt);                      carstatedrdolst.datasource = statedt;                     carstatedrdolst.datatextfield = "state";                      carstatedrdolst.databind();                 }                  carstatedrdolst.items.insert(0, new listitem("select state", ""));             }         } 

}

i think need values of cookie

httpcookie cookie = request.cookies["location"];  if(cookie != null) {      object countryname= cookie.value; } else {      //handle null }