PayPal.OAuthTokenCredential.GenerateOAuthToken C# (CSharp) Method

        private string GenerateOAuthToken(string base64ClientId)
        {
            string response = null;

            Uri uniformResourceIdentifier = null;
            Uri baseUri = null;
            if (config.ContainsKey(BaseConstants.OAuthEndpoint))
            {
                baseUri = new Uri(config[BaseConstants.OAuthEndpoint]);
            }
            else if (config.ContainsKey(BaseConstants.EndpointConfig))
            {
                baseUri = new Uri(config[BaseConstants.EndpointConfig]);
            }
            else if (config.ContainsKey(BaseConstants.ApplicationModeConfig))
            {
                string mode = config[BaseConstants.ApplicationModeConfig];
                if (mode.Equals(BaseConstants.LiveMode))
                {
                    baseUri = new Uri(BaseConstants.RESTLiveEndpoint);
                }
                else if (mode.Equals(BaseConstants.SandboxMode))
                {
                    baseUri = new Uri(BaseConstants.RESTSandboxEndpoint);
                }
                else if (mode.Equals(BaseConstants.TestSandboxMode))
                {
                    baseUri = new Uri(BaseConstants.RESTTestSandboxEndpoint);
                }
                else
                {
                    throw new ConfigException("You must specify one of mode(live/sandbox) OR endpoint in the configuration");
                }
            }
            bool success = Uri.TryCreate(baseUri, OAuthTokenPath, out uniformResourceIdentifier);
            ConnectionManager connManager = ConnectionManager.Instance;
                HttpWebRequest httpRequest = connManager.GetConnection(this.config, uniformResourceIdentifier.AbsoluteUri);

            Dictionary<string, string> headers = new Dictionary<string, string>();
            headers.Add("Authorization", "Basic " + base64ClientId);
            string postRequest = "grant_type=client_credentials";
            httpRequest.Method = "POST";
            httpRequest.Accept = "*/*";
            httpRequest.ContentType = "application/x-www-form-urlencoded";
            UserAgentHeader userAgentHeader = new UserAgentHeader(SdkVersion == null ? "" : SdkVersion.GetSDKId(), SdkVersion == null ? "" : SdkVersion.GetSDKVersion());
            Dictionary<string, string> userAgentMap = userAgentHeader.GetHeader();
            foreach (KeyValuePair<string, string> entry in userAgentMap)
            {
                // aganzha
                //iso-8859-1
                Encoding iso8851 = Encoding.GetEncoding("iso-8859-1", new EncoderReplacementFallback(string.Empty), new DecoderExceptionFallback());
                byte[] bytes = Encoding.Convert(Encoding.UTF8,iso8851, Encoding.UTF8.GetBytes(entry.Value));
                httpRequest.UserAgent = iso8851.GetString(bytes);
            }
            foreach (KeyValuePair<string, string> header in headers)
            {
                httpRequest.Headers.Add(header.Key, header.Value);
            }

            HttpConnection httpConnection = new HttpConnection(config);
            try
            {
                response = httpConnection.Execute(postRequest, httpRequest);
            }
            catch (PayPal.Exception.HttpException ex)
            {
                // If we get an HTTP exception back and the status code is 401,
                // then try and generate an IdentityException object to throw.
                if (ex.StatusCode == HttpStatusCode.Unauthorized)
                {
                    IdentityException identityEx;
                    if (ex.TryConvertTo<IdentityException>(out identityEx))
                    {
                        throw identityEx;
                    }
                }

                throw;
            }

            JObject deserializedObject = (JObject)JsonConvert.DeserializeObject(response);
            string generatedToken = (string)deserializedObject["token_type"] + " " + (string)deserializedObject["access_token"];
            this.ApplicationId = (string)deserializedObject["app_id"];
            this.AccessTokenExpirationInSeconds = (int)deserializedObject["expires_in"];
            this.AccessTokenLastCreationDate = DateTime.Now;
            return generatedToken;
        }