API Facebook

I know there are a lot of information about working with Facebook API, but… I just think more information is better then less.

I need to post different types of context to Facebook pages (user create his own page, give us the name of page). OK, let’s go!

I m using ASP.NET MVC, you know… Link to the project.

All events has been shown on the main page.

1. Create our application in facebook.

You see there is secret key and application key. We need them to working with facebook through our application.

1. Authorization (OAuth 2.0).

• Ask user to permission.
• User will be redirected to facebook access page.
• User give us needed permission.
• User has been redirected back to our web site with special code.

There is the step 4 (we get the code from redirecting response).

public void GetAccessToken()
{
    if (HttpContext.Current.Request.Params.AllKeys.Contains("code"))
    {
        code = HttpContext.Current.Request.Params["code"];
        //get the short-lived user access_toke
        string request = string.Format(_tokenEndpoint, _applicationId, _redirectTo, _applicationSecret, code);
        var webClient = new WebClient();
        string response = webClient.DownloadString(request);
        string[] pairResponse = response.Split('&');
        accessToken = pairResponse[0].Split('=')[1];
        //get the long-lived user access_toke
        request = string.Format(_exchangeAccessToken, _applicationId, _applicationSecret, accessToken);
        webClient = new WebClient();
        response = webClient.DownloadString(request);
        if (!accessToken.Equals(response.Split('=')[1]))
        {
            throw new AccessViolationException();
        }
        GetUserInformation();
    }
    else if (HttpContext.Current.Request.Params.AllKeys.Contains("error"))
    {
        error = HttpContext.Current.Request.Params["error"];
        throw new AccessViolationException(error);
    }
    throw new HttpException();
}

That is my facebook controller

public ActionResult Index()
{
    if (!Client.IsAuthorizated)
    {
        return Redirect(Client.UriToAuth);
    }
    return View(new FacebookModel {Name = ""});
}

public ActionResult Authorizate()
{
    Client.GetAccessToken();
    return RedirectToAction("Index");
}

After getting code we need to get the id of the page:

private void GetUserInformation()
{
    string request = "https://graph.facebook.com/me?access_token=" + accessToken;
    var webClient = new WebClient();
    string response = webClient.DownloadString(request);
    user = JObject.Parse(response);
    GetPagesInformation();
}

private void GetPagesInformation()
{
    string request = "https://graph.facebook.com/" + user.SelectToken("id") + "/accounts?access_token=" +
                        accessToken;
    var webClient = new WebClient();
    string response = webClient.DownloadString(request);
    userPages = JObject.Parse(response);
    page = userPages.SelectToken("data").First(x => x.SelectToken("name").ToString().Equals(_pageName));
}

1. OK, let’s start to posting something. Here is my configuration:

private static readonly Dictionary<string, string> Config = new Dictionary<string, string>
{
    {"AuthorizationEndpoint", "https://graph.facebook.com/oauth/authorize?client_id={0}&redirect_uri={1}&scope=manage_pages,create_event,publish_stream"},
    {"TokenEndpoint", "https://graph.facebook.com/oauth/access_token?client_id={0}&redirect_uri={1}&client_secret={2}&code={3}"},
    {"ApplicationId", "387222228001291"},
    {"ApplicationSecret", "3a177e2231e2966733771775b42"},
    {"RedirectTo", "http://localhost:4769/Facebook/Authorizate"},
    {"PageName", "TesterMyRest Community"}
};

Posting video.

public string CreateVideo(MemoryStream imageMemoryStream, string title, string fileName)
{
    string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
    var uploadRequest =
        (HttpWebRequest)
        WebRequest.Create("https://graph.facebook.com/" + page.SelectToken("id") + "/videos?access_token=" +
                            page.SelectToken("access_token"));
    uploadRequest.ServicePoint.Expect100Continue = false;
    uploadRequest.Method = "POST";
    uploadRequest.UserAgent = "Mozilla/4.0 (compatible; Windows NT)";
    uploadRequest.ContentType = "multipart/form-data; boundary=" + boundary;
    uploadRequest.KeepAlive = false;

    var sb = new StringBuilder();

    const string formdataTemplate = "--{0}\r\nContent-Disposition: form-data; name=\"{1}\"\r\n\r\n{2}\r\n";
    sb.AppendFormat(formdataTemplate, boundary, "title", HttpContext.Current.Server.HtmlEncode(title));

    const string headerTemplate = "--{0}\r\nContent-Disposition: form-data; name=\"{1}\"; filename=\"{2}\"\r\nContent-Type: {3}\r\n\r\n";
    sb.AppendFormat(headerTemplate, boundary, "source", fileName, @"application/octet-stream");

    string formString = sb.ToString();
    byte[] formBytes = Encoding.UTF8.GetBytes(formString);
    byte[] trailingBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");

    long imageLength = imageMemoryStream.Length;
    long contentLength = formBytes.Length + imageLength + trailingBytes.Length;
    uploadRequest.ContentLength = contentLength;

    uploadRequest.AllowWriteStreamBuffering = false;
    Stream strmOut = uploadRequest.GetRequestStream();

    strmOut.Write(formBytes, 0, formBytes.Length);

    var buffer = new Byte[checked((uint) Math.Min(4096, (int) imageLength))];
    int bytesRead;
    imageMemoryStream.Seek(0, SeekOrigin.Begin);
    while ((bytesRead = imageMemoryStream.Read(buffer, 0, buffer.Length)) != 0)
    {
        strmOut.Write(buffer, 0, bytesRead);
    }

    strmOut.Write(trailingBytes, 0, trailingBytes.Length);

    strmOut.Close();

    var wresp = uploadRequest.GetResponse() as HttpWebResponse;
    Encoding enc = Encoding.UTF8;
    if (wresp != null)
    {
        var stream = wresp.GetResponseStream();
        if (stream != null)
        {
            var loResponseStream = new StreamReader(stream, enc);
            return "https://graph.facebook.com/" + loResponseStream.ReadToEnd();
        }
    }
    return string.Empty;
}

1. Change the information about the page.

WebHelper class:

public static class WebWorker
{
    private static void AddPostParameter(Dictionary<string, string> values, StringBuilder postBody)
    {
        foreach (string key in values.Keys)
        {
            if (postBody.Length > 0)
            {
                postBody.Append("&");
            }
            postBody.Append(string.Format("{0}={1}", key, values[key]));
        }
    }

    public static JObject DownloadJson(string requestUrl)
    {
        var webClient = new WebClient();
        string response = webClient.DownloadString(requestUrl);
        return JObject.Parse(response);
    }

    public static string UploadString(string requstUrl, Dictionary<string, string> values)
    {
        var webClient = new WebClient();
        var postBody = new StringBuilder();
        AddPostParameter(values, postBody);
        return webClient.UploadString(requstUrl, postBody.ToString());
    }
}

private string CreateStatus(Dictionary<string, string> values)
{
    string request = "https://graph.facebook.com/" + page.SelectToken("id") + "/feed?access_token=" +
                        page.SelectToken("access_token");
    return WebWorker.UploadString(request, values);
}