我是这样做的:

using (HttpClient httpClient = new HttpClient())
{
   Dictionary<string, string> tokenDetails = null;
   var messageDetails = new Message { Id = 4, Message1 = des };
   HttpClient client = new HttpClient();
   client.BaseAddress = new Uri("http://localhost:3774/");
   var login = new Dictionary<string, string>
       {
           {"grant_type", "password"},
           {"username", "sa@role.com"},
           {"password", "lopzwsx@23"},
       };
   var response = client.PostAsync("Token", new FormUrlEncodedContent(login)).Result;
   if (response.IsSuccessStatusCode)
   {
      tokenDetails = JsonConvert.DeserializeObject<Dictionary<string, string>>(response.Content.ReadAsStringAsync().Result);
      if (tokenDetails != null && tokenDetails.Any())
      {
         var tokenNo = tokenDetails.FirstOrDefault().Value;
         client.DefaultRequestHeaders.Add("Authorization", "Bearer " + tokenNo);
         client.PostAsJsonAsync("api/menu", messageDetails)
             .ContinueWith((postTask) => postTask.Result.EnsureSuccessStatusCode());
      }
   }
}

这个you-tube视频帮了我大忙。请查看一下。 https://www.youtube.com/watch?v=qCwnU06NV5Q

对于性能和端口耗尽问题，重用HttpClient实例是一个很好的实践，而且因为没有一个答案给出了这个解决方案(甚至会把你引向糟糕的实践:)，所以我在这里放了一个链接，指向我对类似问题的回答:

https://stackoverflow.com/a/40707446/717372

一些关于如何正确使用HttpClient的源代码:

https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/ https://blogs.msdn.microsoft.com/alazarev/2017/12/29/disposable-finalizers-and-httpclient/

Oauth流程是复杂的，总是有一个或另一个错误的空间。 我的建议是始终使用样板代码和一组用于OAuth身份验证流的库。这会让你的生活更轻松。

下面是库集的链接。用于。net的OAuth库

这可以工作，如果你从服务接收到一个json或xml，我认为这可以给你一个关于标题和T类型如何工作的想法，如果你使用函数MakeXmlRequest(把结果放在xmldocumentnet)和MakeJsonRequest(把json放在类你希望有相同的结构，json响应)在下一种方式

/*-------------------------example of use-------------*/
MakeXmlRequest<XmlDocument>("your_uri",result=>your_xmlDocument_variable =     result,error=>your_exception_Var = error);

MakeJsonRequest<classwhateveryouwant>("your_uri",result=>your_classwhateveryouwant_variable=result,error=>your_exception_Var=error)
/*-------------------------------------------------------------------------------*/


public class RestService
{
    public void MakeXmlRequest<T>(string uri, Action<XmlDocument> successAction, Action<Exception> errorAction)
    {
        XmlDocument XMLResponse = new XmlDocument();
        string wufooAPIKey = ""; /*or username as well*/
        string password = "";
        StringBuilder url = new StringBuilder();
        url.Append(uri);
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url.ToString());
        string authInfo = wufooAPIKey + ":" + password;
        authInfo = Convert.ToBase64String(Encoding.Default.GetBytes(authInfo));
        request.Timeout = 30000;
        request.KeepAlive = false;
        request.Headers["Authorization"] = "Basic " + authInfo;
        string documento = "";
        MakeRequest(request,response=> documento = response,
                            (error) =>
                            {
                             if (errorAction != null)
                             {
                                errorAction(error);
                             }
                            }
                   );
        XMLResponse.LoadXml(documento);
        successAction(XMLResponse);
    }



    public void MakeJsonRequest<T>(string uri, Action<T> successAction, Action<Exception> errorAction)
    {
        string wufooAPIKey = "";
        string password = "";
        StringBuilder url = new StringBuilder();
        url.Append(uri);
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url.ToString());
        string authInfo = wufooAPIKey + ":" + password;
        authInfo = Convert.ToBase64String(Encoding.Default.GetBytes(authInfo));
        request.Timeout = 30000;
        request.KeepAlive = false;
        request.Headers["Authorization"] = "Basic " + authInfo;
       // request.Accept = "application/json";
      //  request.Method = "GET";
        MakeRequest(
           request,
           (response) =>
           {
               if (successAction != null)
               {
                   T toReturn;
                   try
                   {
                       toReturn = Deserialize<T>(response);
                   }
                   catch (Exception ex)
                   {
                       errorAction(ex);
                       return;
                   }
                   successAction(toReturn);
               }
           },
           (error) =>
           {
               if (errorAction != null)
               {
                   errorAction(error);
               }
           }
        );
    }
    private void MakeRequest(HttpWebRequest request, Action<string> successAction, Action<Exception> errorAction)
    {
        try{
            using (var webResponse = (HttpWebResponse)request.GetResponse())
            {
                using (var reader = new StreamReader(webResponse.GetResponseStream()))
                {
                    var objText = reader.ReadToEnd();
                    successAction(objText);
                }
            }
        }catch(HttpException ex){
            errorAction(ex);
        }
    }
    private T Deserialize<T>(string responseBody)
    {
        try
        {
            var toReturns = JsonConvert.DeserializeObject<T>(responseBody);
             return toReturns;
        }
        catch (Exception ex)
        {
            string errores;
            errores = ex.Message;
        }
        var toReturn = JsonConvert.DeserializeObject<T>(responseBody);
        return toReturn;
    }
}
}

static async Task<AccessToken> GetToken()
{
        string clientId = "XXX";
        string clientSecret = "YYY";
        string credentials = String.Format("{0}:{1}", clientId, clientSecret);

        using (var client = new HttpClient())
        {
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(Encoding.UTF8.GetBytes(credentials)));
            List<KeyValuePair<string, string>> requestData = new List<KeyValuePair<string, string>>();
            requestData.Add(new KeyValuePair<string, string>("grant_type", "client_credentials"));
            FormUrlEncodedContent requestBody = new FormUrlEncodedContent(requestData);
            var request = await client.PostAsync("https://accounts.spotify.com/api/token", requestBody);
            var response = await request.Content.ReadAsStringAsync();
            return JsonConvert.DeserializeObject<AccessToken>(response);
        }
    }

这可能有助于设置标题:

WebClient client = new WebClient();

string authInfo = this.credentials.UserName + ":" + this.credentials.Password;
authInfo = Convert.ToBase64String(Encoding.Default.GetBytes(authInfo));
client.Headers["Authorization"] = "Basic " + authInfo;