C# post 方式调用 webservice

int pageSize = 500;
int total = pageSize;
DataTable _dt = new DataTable();
//循环调用 webservice 直至取完所有数据.
for (int i = 1; i <= Math.Ceiling((double)(total * 1.0 / pageSize)); i++)
{

                            //要调用webservice 的地址
                            string _url = "http://url";

//生成一个实例

                            var request = (HttpWebRequest)WebRequest.Create(_url);

                            //Header增加参数以键值对方式增加: key:value
                            request.Headers.Add("Authorization", Authorization);
                            //内容类型
                            request.ContentType = "application/json";
                            //提交方式
                            request.Method = "POST";

                            using (var streamWriter = new StreamWriter(request.GetRequestStream()))
                            {
                                //设置发送的body json 参数
                                string json = new JavaScriptSerializer().Serialize(new
                                {
                                    filter = new
                                    {
                                        startDate = "",
                                        endDate = "",
                                        Code = ""
                                    },
                                    pageIndex = i,
                                    pageSize = pageSize
                                });

                                //GetRequestStream 方法返回用于发送 HttpWebRequest 数据的流。返回 Stream 对象后，可以通过使用 Stream.Write 方法发送带有 HttpWebRequest 的数据。
                                streamWriter.Write(json);
                            }

                            //创建接收实例
                            var response = (HttpWebResponse)request.GetResponse();

                            //接收响应
                            using (var streamReader = new StreamReader(response.GetResponseStream()))
                            {
                                //响应字符串
                                string retString = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding("utf-8")).ReadToEnd();

                                Newtonsoft.Json.Linq.JObject jobject = (Newtonsoft.Json.Linq.JObject)JsonConvert.DeserializeObject(retString);

                                //处理返回值中的total 属性 赋值给 原total 这里才是准确的 total
                                total = Convert.ToInt32(jobject["data"]["total"].ToString());
                                //调用 PrivateMethods.JsonToDataTable 方法直接把 返回 json 串中 数组转换成了 datatable.
                                DataTable temp = PrivateMethods.JsonToDataTable(retString);
                                //把本次获取到的数据,插入到 _dt 表中.

                                foreach (DataRow dr in temp.Rows) { _dt.ImportRow(dr); }
                            }
}