用 C# 上传 Facebook 照片？

Question

我正在尝试使用 Facebook Graph API 从 Windows Phone Silverlight 应用程序将照片上传到 Facebook，但收到错误：(#324) 需要上传文件。任何人都可以看到我的代码有什么问题吗？

    internal void PublishPhoto(System.IO.MemoryStream stream, string message, string accessToken)
    {
        var requestUriString = string.Format(
            CultureInfo.InvariantCulture, 
            "https://graph.facebook.com/{0}/photos?access_token={1}&message={2}",
            "me",
            accessToken,
            message);

        var webRequest = WebRequest.CreateHttp(requestUriString);

        webRequest.Method = "POST";

        var boundary = "7db3d9202a1";
        webRequest.ContentType = string.Format("multipart/form-data; boundary={0}", boundary);

        webRequest.BeginGetRequestStream(new AsyncCallback(delegate (IAsyncResult result)
            {
                GetRequestStream(stream, boundary, result);

                BeginGetResponse(webRequest);

            }), webRequest);
    }

    private static void GetRequestStream(System.IO.MemoryStream imageStream, string boundary, IAsyncResult result)
    {
        var webRequest2 = result.AsyncState as HttpWebRequest;

        using (var requestStream = webRequest2.EndGetRequestStream(result))
        {
            using (StreamWriter writer = new StreamWriter(requestStream))
            {
                writer.WriteLine("--{0}\r", boundary);
                writer.WriteLine("Content-Disposition: form-data; filename=\"sketch.jpg\"\r");
                writer.WriteLine("Content-Type: image/jpg\r");

                byte[] buffer = imageStream.GetBuffer();
                requestStream.Write(buffer, 0, buffer.Length);

                writer.WriteLine("\r");
                writer.WriteLine("--{0}--\r", boundary);
            }

            imageStream.Close();
        }
    }

    private static void BeginGetResponse(HttpWebRequest webRequest)
    {
        webRequest.BeginGetResponse(new AsyncCallback(delegate(IAsyncResult result2)
        {
            var webRequest2 = result2.AsyncState as HttpWebRequest;

            try
            {
                using (var response = webRequest2.EndGetResponse(result2))
                {
                    using (var responseStream = response.GetResponseStream())
                    {
                        using (StreamReader reader = new StreamReader(responseStream))
                        {
                            System.Diagnostics.Debug.WriteLine(reader.ReadToEnd());
                        }
                    }
                }
            }
            catch (WebException we)
            {
                System.Diagnostics.Debug.WriteLine(we.Message);

                using (var responseStream = we.Response.GetResponseStream())
                {
                    using (StreamReader reader = new StreamReader(responseStream))
                    {
                        var errorJson = reader.ReadToEnd();

                        var response = Newtonsoft.Json.JsonConvert.DeserializeObject<FacebookErrorResponse>(errorJson);

                        System.Diagnostics.Debug.WriteLine("Could not upload image to Facebook: {0}", response.Error.Message);
                    }
                }
            }
        }), webRequest);
    }
}

Answer 1

尝试在 Content-Disposition 标头中指定“源”名称以及文件名，即

writer.WriteLine("Content-Disposition: form-data; name=\"source\"; filename=\"sketch.jpg\"\r");

Answer 2

好吧，我第一次错了，但现在我明白了。

我们上面已经解决的第一个问题是，您在 POST 正文中缺少每个边界之前的“--”以及最后一个边界之后的“--”。

第二个问题是，在写入图像内容之前，您没有在 MIME 标头后面留下空行。

第三个问题是，在将图像数据写入其底层流之前，您没有刷新写入器（除非手机上的 silverlight 与自动刷新 StreamWriter 中的普通 .NET 不同）。

总而言之，这应该有效：

            writer.WriteLine("--{0}\r", boundary);
            writer.WriteLine("Content-Disposition: form-data; filename=\"sketch.jpg\"\r");
            writer.WriteLine("Content-Type: image/jpg\r");
            writer.WriteLine("\r");
            writer.Flush();

            byte[] buffer = imageStream.GetBuffer();
            requestStream.Write(buffer, 0, buffer.Length);

            writer.WriteLine("\r");
            writer.WriteLine("--{0}--\r", boundary);