URLConnection未完成获取InputStream

Question

我创建一个到身份验证服务器（OAuth 2.0）的连接来获取令牌。这样做的方法如下：

public static async Task<String> GetToken(string username, string password)
        {
            String response = null;
            await Task.Run(() =>
            {
                URL url = new URL(Configuration.Configuration.baseURL + Configuration.Configuration.tokenPath);
                HttpURLConnection urlConnection = (HttpURLConnection)url.OpenConnection();
                urlConnection.DoOutput = true;
                urlConnection.DoInput = true;
                urlConnection.RequestMethod = "POST";
                urlConnection.SetRequestProperty("Content-Type", "application/x-www-form-urlencoded");
                var content = new FormUrlEncodedContent(new[]
                {
                    new KeyValuePair<string, string>("grant_type", "password"),
                    new KeyValuePair<string, string>("username", username),
                    new KeyValuePair<string, string>("password", password),
                    new KeyValuePair<string, string>("client_id", "widas_servicebar"),
                    new KeyValuePair<string, string>("scope", Configuration.Configuration.scopes)
                });
                //var content = new Dictionary<string, string>();
                //content.Add("grant_type", "password");
                //content.Add("username", username);
                //content.Add("password", password);
                //content.Add("client_id", "widas_servicebar");
                //content.Add("scope", Configuration.Configuration.scopes);
                using (var streamWriter = new StreamWriter(urlConnection.OutputStream))
                {
                    streamWriter.Write(content);
                    streamWriter.Flush();
                    streamWriter.Close();
                }
                urlConnection.Connect();
                var stream = urlConnection.InputStream;
                using (var streamReader = new StreamReader(stream))
                {
                    response = streamReader.ReadToEnd();                    
                    return response;
                }
            });
            return response;
        }

不幸的是，当我调试代码时，它总是被困在var stream = urlConnection.InputStream;，从那以后什么都没有发生（我尝试等待15分钟，使用Postman，请求在200-500ms内得到响应）。

我在其他一些方法中使用了几乎相同的代码，这些方法也建立了与服务器（内容服务器）的连接，并且工作正常。

我的代码中有错误吗？或者输入流永远不会结束的原因是什么？

如果有什么重要的话：我正在构建一个Xamarin.Android项目。

Answer 1

以防万一：有一个名为Xamarin.Auth的Xamarin组件提供OAuth身份验证。你不必手动实现：

Xamnarin.Forms教程：https://developer.xamarin.com/guides/xamarin-forms/web-services/authentication/oauth/

NuGet：https://www.nuget.org/packages/Xamarin.Auth/

Answer 2

我开始工作了。我尝试使用的东西似乎并没有像我想象的那样奏效。现在工作的代码如下：

public static async Task<String> GetToken(string username, string password)
        {
            String response = null;
            await Task.Run(() =>
            {
                URL url = new URL(Configuration.Configuration.baseURL + Configuration.Configuration.tokenPath);
                HttpURLConnection urlConnection = (HttpURLConnection)url.OpenConnection();
                urlConnection.DoOutput = true;
                urlConnection.DoInput = true;
                urlConnection.RequestMethod = "POST";
                urlConnection.SetRequestProperty("Content-Type", "application/x-www-form-urlencoded");                            
                var content = new Dictionary<string, string>();
                content.Add("grant_type", "password");
                content.Add("username", username);
                content.Add("password", password);
                content.Add("client_id", "widas_servicebar");
                content.Add("scope", Configuration.Configuration.scopes);
                Stream os = urlConnection.OutputStream;
                BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
                writer.Write(getQuery(content));
                writer.Flush();
                writer.Close();
                os.Close();
                urlConnection.Connect();
                //var debug = urlConnection.ErrorStream;
                var stream = urlConnection.InputStream;
                using (var streamReader = new StreamReader(stream))
                {
                    response = streamReader.ReadToEnd();                    
                }
                return response;
            });
            return response;
        }

getQuery方法如下所示：

private static String getQuery(Dictionary<string, string> dictionary)
        {
            StringBuilder result = new StringBuilder();
            bool first = true;
            foreach (KeyValuePair<string, string> entry in dictionary)
            {      
                if (first)
                {
                    first = false;
                }          
                result.Append(URLEncoder.Encode(entry.Key, "UTF-8"));
                result.Append("=");
                result.Append(URLEncoder.Encode(entry.Value, "UTF-8"));
                result.Append("&");
            }
            return result.ToString();
        }