Echosign RestAPI Access Token Generation in C#

Hi All,

I have download the Echosign Rest Client API and consume the same in my Asp.Net web application. Can you tell me, How to create Access Token? I have passed the required parameter to below method but Access token is null.

/// <summary>

        /// Initialize EchosignREST without Access Token. Must call Authorize() after initialization to acquire Access Token.

        /// </summary>

        /// <param name="apiUrl">API url returned from the authorization request URL</param>

        /// <param name="clientId">Application/Client ID</param>

        /// <param name="secretId">Client Secret</param>

public EchosignREST(string apiUrl, string clientId, string secretId)

        {

            this.apiUrl = apiUrl;

            this.clientId = clientId;

            this.secretId = secretId;

            client = new HttpClient();

            client.BaseAddress = new Uri(apiUrl);

        }

How to access below method without creating Access Token by above method?

/// <summary>

        /// Obtain Access Token for the Echosign REST API (use only if you don't already have a Refresh Token, or if it is expired)

        /// </summary>

        /// <param name="authCode">Authorization code received from the authorization request</param>

        /// <param name="redirect_uri">Redirect URI matching the one specified in the authorization request</param>

        /// <returns></returns>

        public async Task Authorize(string authCode, string redirect_uri)

        {

            using (HttpContent content = new FormUrlEncodedContent(new List<KeyValuePair<string, string>>

            {

                new KeyValuePair<string, string>("grant_type", "authorization_code"),

                new KeyValuePair<string, string>("client_id", clientId),

                new KeyValuePair<string, string>("client_secret", secretId),

                new KeyValuePair<string, string>("code", authCode),

                new KeyValuePair<string, string>("redirect_uri", redirect_uri)

            }))

            {

                HttpResponseMessage result = await client.PostAsync("oauth/token", content).ConfigureAwait(false);

                if (result.IsSuccessStatusCode)

                {

                    string response = await result.Content.ReadAsStringAsync();

                    TokenResponse tokenObj = JsonConvert.DeserializeObject<TokenResponse>(response);

                    this.accessToken = tokenObj.access_token;

                    this.accessTokenExpires = tokenObj.expires_in;

                    this.refreshToken = tokenObj.refresh_token;

                    client.DefaultRequestHeaders.Remove("Access-Token");

                    client.DefaultRequestHeaders.Add("Access-Token", accessToken);

                }

                else

                {

                    string response = await result.Content.ReadAsStringAsync().ConfigureAwait(false);

                    HandleError(result.StatusCode, response, true);

                }

            }

        }

Thanks & Regards

Poomani Sankaran