c#post头有关问题

c#post头问题
POST /hospital/hospitalsearch/list.json HTTP/1.1
User-Agent: android
version: 2.34
appid: p_android_weiyi
version-type: patient
os-token-id: 7c5280e3-23cf-466b-afad-d8d6edb87f4a
sign: UzzEyNJMwZlhR7pet6Swt0SxhQFxVcsqLFhki1MN4uWLoeKnCl5gIxpb3dwgK1v5MLLTaSwSsGWsodbJn5/GMaHhOUf6Wk7T3hJIei+Qm+VWQ/V2fv0VbEjl4ijKI+Fgh7JslaLDvI5CP9PONBEV6I/9iVzkGD1OGSOAHYNcT5g=
Content-Type: application/json
Content-Length: 71
Host: mobileservice.guahao.cn
Connection: Keep-Alive
Expect: 100-continue

{"pageNo":1,"pageSize":20,"sort":"region_sort","area":"79","haoyuan":2}


c#代码
string strUrl = "http://mobileservice.guahao.cn/hospital/hospitalsearch/list.json";
            HttpWebRequest httpWebRequest = null;
            HttpWebResponse httpWebRespones = null;
            string strHtml;
            httpWebRequest = (HttpWebRequest)WebRequest.Create(strUrl);
            httpWebRequest.AllowAutoRedirect = true;
            httpWebRequest.UserAgent = "android";
            httpWebRequest.Method = "post";
            httpWebRequest.KeepAlive = true;
            httpWebRequest.AllowAutoRedirect = false;
            httpWebRequest.ContentType = "application/json";
            httpWebRequest.Headers.Add("version", "2.34");
            httpWebRequest.Headers.Add("appid", "p_android_weiyi");
            httpWebRequest.Headers.Add("version-type", "patient");
            httpWebRequest.Headers.Add("sign", "UzzEyNJMwZlhR7pet6Swt0SxhQFxVcsqLFhki1MN4uWLoeKnCl5gIxpb3dwgK1v5MLLTaSwSsGWsodbJn5/GMaHhOUf6Wk7T3hJIei+Qm+VWQ/V2fv0VbEjl4ijKI+Fgh7JslaLDvI5CP9PONBEV6I/9iVzkGD1OGSOAHYNcT5g=");

            string postDataStr = @"{""pageNo"":1,""pageSize"":10,""sort"":""department"",""department"":""2b7ac3ed-6cad-4307-93a4-1b111c5e182e000"",""dynamicFilter"":1}";
            byte[] postdatabytes = Encoding.UTF8.GetBytes(postDataStr);
            Stream writer;
            writer = httpWebRequest.GetRequestStream();
            writer.Write(postdatabytes, 0, postdatabytes.Length);
            writer.Flush();
            writer.Close();
            
            httpWebRespones = (HttpWebResponse)httpWebRequest.GetResponse();

            using (Stream stream = httpWebRespones.GetResponseStream())
            {
                using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                {
                    strHtml = reader.ReadToEnd();
                }
            } 

麻烦看下是否头信息不对，我用php试过是可以访问的
------解决思路----------------------
http头应该没问题，关键的是你post的参数是否正确，这个你要跟后台一起调试一下