使用 Graph API 将图像从 .NET 发布到 Facebook 墙上

Question

我正在使用 Facebook 的 Javascript API 开发一个需要能够将图像发布到用户墙上的应用程序。 据我所知，应用程序的该部分需要在服务器端，因为它需要将图像数据发布为“multipart/form-data”。

注意：不是使用“post”的简单版本，而是真正的“photos”方法。

http://graph.facebook.com/me/photos

我认为我面临两个问题，一个 .NET 和一个 Facebook 问题：

Facebook 问题：我不太确定是否所有参数都应作为 multipart/form-data（包括 access_token 和消息）发送。唯一的代码示例使用 cUrl util/application。

.NET 问题：我从未从 .NET 发出 multipart/form-data 请求，我不确定 .NET 是否会自动创建 mime-parts，或者我是否必须进行编码以某种特殊方式的参数。

调试有点困难，因为我从 Graph API 得到的唯一错误响应是“400 - 错误请求”。 下面是我决定写这个问题时的代码（是的，它有点冗长:-)

最终的答案当然是从 .NET 发布图像的示例 sn-p，但我可以接受更少。

string username = null;
string password = null;
int timeout = 5000;
string requestCharset = "UTF-8";
string responseCharset = "UTF-8";
string parameters = "";
string responseContent = "";

string finishedUrl = "https://graph.facebook.com/me/photos";

parameters = "access_token=" + facebookAccessToken + "&message=This+is+an+image";
HttpWebRequest request = null;
request = (HttpWebRequest)WebRequest.Create(finishedUrl);
request.Method = "POST";
request.KeepAlive = false;
//application/x-www-form-urlencoded | multipart/form-data
request.ContentType = "multipart/form-data";
request.Timeout = timeout;
request.AllowAutoRedirect = false;
if (username != null && username != "" && password != null && password != "")
{
    request.PreAuthenticate = true;
    request.Credentials = new NetworkCredential(username, password).GetCredential(new Uri(finishedUrl), "Basic");
}
//write parameters to request body
Stream requestBodyStream = request.GetRequestStream();
Encoding requestParameterEncoding = Encoding.GetEncoding(requestCharset);
byte[] parametersForBody = requestParameterEncoding.GetBytes(parameters);
requestBodyStream.Write(parametersForBody, 0, parametersForBody.Length);
/*
This wont work
byte[] startParm = requestParameterEncoding.GetBytes("&source=");
requestBodyStream.Write(startParm, 0, startParm.Length);
byte[] fileBytes = File.ReadAllBytes(Server.MapPath("images/sample.jpg"));
requestBodyStream.Write( fileBytes, 0, fileBytes.Length );
*/
requestBodyStream.Close();

HttpWebResponse response = null;
Stream receiveStream = null;
StreamReader readStream = null;
Encoding responseEncoding = System.Text.Encoding.GetEncoding(responseCharset);
try 
{
    response = (HttpWebResponse) request.GetResponse();
    receiveStream = response.GetResponseStream();
    readStream = new StreamReader( receiveStream, responseEncoding );
    responseContent = readStream.ReadToEnd();
}
finally 
{
    if (receiveStream != null)
    {
        receiveStream.Close();
    }
    if (readStream != null)
    {
        readStream.Close();
    }
    if (response != null)
    {
        response.Close();
    }
}

Answer 1

这里是如何上传二进制数据的示例。但是上传到 /me/photos 不会将图像发布到墙上 :( 图像保存到您的应用程序的相册中。我不知道如何在提要中宣布它。另一种方法是将图像发布到“墙相册”，通过 URL=="graph.facebook.com/%wall-album-id%/photos"。但没有找到任何方法来创建这样的相册（用户在上传图片来自网站）。

{
    string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
    uploadRequest = (HttpWebRequest)WebRequest.Create(@"https://graph.facebook.com/me/photos");
    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;

    StringBuilder sb = new StringBuilder();

    string formdataTemplate = "--{0}\r\nContent-Disposition: form-data; name=\"{1}\"\r\n\r\n{2}\r\n";
    sb.AppendFormat(formdataTemplate, boundary, "access_token", PercentEncode(facebookAccessToken));
    sb.AppendFormat(formdataTemplate, boundary, "message", PercentEncode("This is an image"));

    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", "file.png", @"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 strm_out = uploadRequest.GetRequestStream();

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

    byte[] buffer = new Byte[checked((uint)Math.Min(4096, (int)imageLength))];
    int bytesRead = 0;
    int bytesTotal = 0;
    imageMemoryStream.Seek(0, SeekOrigin.Begin);
    while ((bytesRead = imageMemoryStream.Read(buffer, 0, buffer.Length)) != 0)
    {
        strm_out.Write(buffer, 0, bytesRead); bytesTotal += bytesRead;
        gui.OnUploadProgress(this, (int)(bytesTotal * 100 / imageLength));
    }

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

    strm_out.Close();

    HttpWebResponse wresp = uploadRequest.GetResponse() as HttpWebResponse;
}

Answer 2

使用@fitz 的代码清理了类方法。传入图像的字节数组或文件路径。如果上传到现有专辑，则传入专辑 ID。

public string UploadPhoto(string album_id, string message, string filename, Byte[] bytes, string Token)
{
    // Create Boundary
    string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");

    // Create Path
    string Path = @"https://graph.facebook.com/";
    if (!String.IsNullOrEmpty(album_id))
    {
        Path += album_id + "/";
    }
    Path += "photos";

    // Create HttpWebRequest
    HttpWebRequest uploadRequest;
    uploadRequest = (HttpWebRequest)HttpWebRequest.Create(Path);
    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;

    // New String Builder
    StringBuilder sb = new StringBuilder();

    // Add Form Data
    string formdataTemplate = "--{0}\r\nContent-Disposition: form-data; name=\"{1}\"\r\n\r\n{2}\r\n";

    // Access Token
    sb.AppendFormat(formdataTemplate, boundary, "access_token", HttpContext.Current.Server.UrlEncode(Token));

    // Message
    sb.AppendFormat(formdataTemplate, boundary, "message", message);

    // Header
    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");

    // File
    string formString = sb.ToString();
    byte[] formBytes = Encoding.UTF8.GetBytes(formString);
    byte[] trailingBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");
    byte[] image;
    if (bytes == null)
    {
        image = File.ReadAllBytes(HttpContext.Current.Server.MapPath(filename));
    }
    else
    {
        image = bytes; 
    }

    // Memory Stream
    MemoryStream imageMemoryStream = new MemoryStream();
    imageMemoryStream.Write(image, 0, image.Length);

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

    // Get Request Stream
    uploadRequest.AllowWriteStreamBuffering = false;
    Stream strm_out = uploadRequest.GetRequestStream();

    // Write to Stream
    strm_out.Write(formBytes, 0, formBytes.Length);
    byte[] buffer = new Byte[checked((uint)Math.Min(4096, (int)imageLength))];
    int bytesRead = 0;
    int bytesTotal = 0;
    imageMemoryStream.Seek(0, SeekOrigin.Begin);
    while ((bytesRead = imageMemoryStream.Read(buffer, 0, buffer.Length)) != 0)
    {
        strm_out.Write(buffer, 0, bytesRead); bytesTotal += bytesRead;
    }
    strm_out.Write(trailingBytes, 0, trailingBytes.Length);

    // Close Stream
    strm_out.Close();

    // Get Web Response
    HttpWebResponse response = uploadRequest.GetResponse() as HttpWebResponse;

    // Create Stream Reader
    StreamReader reader = new StreamReader(response.GetResponseStream());

    // Return
    return reader.ReadToEnd();
}

Answer 3

您必须使用字节数组自己构造多部分/表单数据。 无论如何，我已经这样做了。您可以通过http://computerbeacon.net/ 查看 Facebook Graph Toolkit。我会在几天内将工具包更新到 0.8 版，其中将包括“将照片发布到 facebook 墙”功能以及其他新功能和更新。

Answer 4

我可以使用RestSharp发布图片：

// url example: https://graph.facebook.com/you/photos?access_token=YOUR_TOKEN
request.AddFile("source", imageAsByteArray, openFileDialog1.SafeFileName, getMimeType(Path.GetExtension(openFileDialog1.FileName)));
request.addParameter("message", "your photos text here");

User API 或 Page API 用于发布照片

How to convert Image to Byte Array

注意：我传递了一个空字符串作为 mime 类型，而 facebook 足够聪明，可以弄清楚。

Answer 5

也许有用

        [TestMethod]
        [DeploymentItem(@".\resources\velas_navidad.gif", @".\")]
        public void Post_to_photos()
        {
            var ImagePath = "velas_navidad.gif";
            Assert.IsTrue(File.Exists(ImagePath));

            var client = new FacebookClient(AccessToken);
            dynamic parameters = new ExpandoObject();

            parameters.message = "Picture_Caption";
            parameters.subject = "test 7979";
            parameters.source = new FacebookMediaObject
{
    ContentType = "image/gif",
    FileName = Path.GetFileName(ImagePath)
}.SetValue(File.ReadAllBytes(ImagePath));

            //// Post the image/picture to User wall
            dynamic result = client.Post("me/photos", parameters);
            //// Post the image/picture to the Page's Wall Photo album
            //fb.Post("/368396933231381/", parameters); //368396933231381 is Album id for that page.

            Thread.Sleep(15000);
            client.Delete(result.id);
        }

参考： Making Requests