How to send the function return that fetches the data from my xml to an input via ajax / jquery?

      try
             {

               XmlDocument xmldoc = new XmlDocument();
               XmlReader reader = new XmlTextReader(Stream.Null);//Stream
               reader.MoveToContent();
               reader.ReadToFollowing("cNF");
               reader.Read();
               return reader.Value;

            if (_NFE_CHAVE_ACESSO.getNFEChaveAcesso(reader.Value) == null)
            {
                var XML = _NFE_CHAVE_ACESSO.getNFEChaveAcesso(reader.Value, 
               );
            }

        }
        catch
        {
            return "";
        }
    }

This code looks for the values that are inside the invoice access key inside the XML, it needed to send this search value to an input that would display this value.