HttpClient

public void UserLogin()
{
using (HttpClient client = new HttpClient())
{
client.DefaultRequestHeaders.Add("Authorization", default_Token);
List<KeyValuePair<String, String>> paramList = new List<KeyValuePair<String, String>>();
paramList.Add(new KeyValuePair<string, string>("grant_type", "password"));
paramList.Add(new KeyValuePair<string, string>("activationCode", "CloudPeak"));
paramList.Add(new KeyValuePair<string, string>("deviceId", "CloudPeak"));
var response = client.PostAsync(serverUrl+"/OAuth/Token", new FormUrlEncodedContent(paramList)).Result;
var str = response.Content.ReadAsStringAsync().Result;

var aa = JObject.Parse(str).ToObject<Dictionary<string, string>>();
string tokenstr = aa["access_token"];
user_Token = "Bearer " + tokenstr;
isUserLogin = true;
//MessageBox.Show(tokenstr);

}
}

public void GetKaipiaoList(string startTime,string endTime,string searchKey)
{
using (HttpClient client = new HttpClient())
{
string urlstr = serverUrl + "/api/services/app/invoiceRecord/GetInvoiceRecordPagedList";

client.DefaultRequestHeaders.Add("Authorization", user_Token);

Dictionary<string, object> dic = new Dictionary<string, object>();
dic.Add("MaxResultCount", "100");
dic.Add("SkipCount", 0);
dic.Add("Sorting", "");
dic.Add("BeginDateTime", "2015-10-01 11:11:11");
dic.Add("EndDateTime", "2016-10-01 11:11:11");
dic.Add("SearchValue", "");
HttpContent content = new StringContent(JsonConvert.SerializeObject(dic));
content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
var response = client.PostAsync(urlstr, content).Result;
var str = response.Content.ReadAsStringAsync().Result;
MessageBox.Show(str);

//var aa = JObject.Parse(str).ToObject<Dictionary<string, string>>();
//string tokenstr = aa["access_token"];
//user_Token = "Bearer " + tokenstr;
//isUserLogin = true;
//MessageBox.Show(tokenstr);

}
}