private static string GetSortedParas(Dictionary<string, string> dic)

 {

     dic = dic.OrderBy(key => key.Key).ToDictionary(keyItem => keyItem.Key, valueItem => valueItem.Value);

     var sbPara = new StringBuilder();

     foreach (var para in dic.Where(para => !para.Value.IsNullOrWhiteSpace()))

     {

         sbPara.AppendFormat("{0}={1}&", para.Key, para.Value);

     }

     return sbPara.ToString().TrimEnd('&');

 }