C#中httpclient的使用

1.使用HttpClient调用Oauth的授权接口获取access_token

1）OAuth使用的密码式

2）获取到access_token后才进行下一步

2.带着access_token调用接口

1）hearder上添加bearer方式的access_token

2）调用接口确保成功获取到返回的结果

  try
            {
                string host = ConfigurationManager.AppSettings["api_host"];
                string username = ConfigurationManager.AppSettings["api_username"];
                string password = ConfigurationManager.AppSettings["api_password"];

                HttpClient httpClient = new HttpClient();

                // 设置请求头信息
                httpClient.DefaultRequestHeaders.Add("Host", host);
                httpClient.DefaultRequestHeaders.Add("Method", "Post");
                httpClient.DefaultRequestHeaders.Add("KeepAlive", "false");   // HTTP KeepAlive设为false，防止HTTP连接保持
                httpClient.DefaultRequestHeaders.Add("UserAgent",
                    "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11");

                //获取token
                var tokenResponse = httpClient.PostAsync("http://" + host + "/token", new FormUrlEncodedContent(new Dictionary<string, string> {
                {"grant_type","password"},
                {"username", username},
                {"password", password}
            }));
                tokenResponse.Wait();
                tokenResponse.Result.EnsureSuccessStatusCode();
                var tokenRes = tokenResponse.Result.Content.ReadAsStringAsync();
                tokenRes.Wait();
                var token = Newtonsoft.Json.Linq.JObject.Parse(tokenRes.Result);
                var access_token = token["access_token"].ToString();

                // 调用接口发起POST请求
                var authenticationHeaderValue = new AuthenticationHeaderValue("bearer", access_token);
                httpClient.DefaultRequestHeaders.Authorization = authenticationHeaderValue;
                var content = new StringContent(parameter);
                content.Headers.ContentType=new MediaTypeHeaderValue("application/json");
                var response = httpClient.PostAsync("http://" + host + "/" + api_address,content );

                response.Wait();
                response.Result.EnsureSuccessStatusCode();
                var res = response.Result.Content.ReadAsStringAsync();
                res.Wait();
                return Newtonsoft.Json.JsonConvert.DeserializeObject<ResultEx>(res.Result);
            }
            catch (Exception ex)
            {

                return ResultEx.Init(ex.Message);
            }