How to upload Pending Attachment to Yammer - httpwebrequest

Question

I'm trying to upload files to yammer via REST Api.
the API say ,i could use
POST https://www.yammer.com/api/v1/messages.json
attachmentn and pending_attachmentn - Yammer provides two methods to associate attachments with a message. Both make use of multi-part HTTP upload (see RFC1867).
then i try to post my message via WebRequest.like this link
but unfortunately, i got "Internal Server Error"[500]. like this question
is anyone could tell me ,how to upload a file to yammer?
and , how to get a pending_attachment list?

Answer 1

Well, finally , I know the reason for the failure .
request format.
RFC 1867say:
Content-type: multipart/form-data, boundary=AaB03x
--AaB03x
content-disposition: form-data; name="field1"
Joe Blow
--AaB03x
content-disposition: form-data; name="pics"; filename="file1.txt"
Content-Type: text/plain
... contents of file1.txt ...
--AaB03x--
there two points
multipart/form-data, boundary=AaB03x ->
multipart/form-data; boundary=AaB03x
no empty line at first line
Content-type: multipart/form-data, boundary=AaB03x
--AaB03x
Content-Disposition: form-data; name="field1"
Joe Blow
--AaB03x
Content-Disposition: form-data; name="pics"; filename="file1.txt"
Content-Type: text/plain
... contents of file1.txt ...
--AaB03x--

Answer 2

I stuck for days just to post message with attachment. I have no idea how to post message with attachmentN, but it is working with pending_attachmentN method.
First you have to call pending_attachment API and get the result ID. Then assign the ID into pending_attachmentN on message API.
I refer to sample as my baseline code. Then I merged with this C# HttpClient 4.5 multipart/form-data upload
Find below code to post message with attachment to Yammer. Hope can save your days.
public static async Task<PendingAttachment> Upload(string FilePath)
{
byte[] byteFile = System.IO.File.ReadAllBytes(FilePath);
FileInfo fi = new FileInfo(FilePath);
PendingAttachment pa = null;
using (var client = new HttpClient())
{
string token = "XXXXXXXXXXXXX";
client.DefaultRequestHeaders.Add("Authorization", "Bearer" + token);
using (var content = new MultipartFormDataContent("Upload----" + DateTime.Now.ToString(CultureInfo.InvariantCulture)))
{
content.Add(new StreamContent(new MemoryStream(byteFile)), "attachment", fi.Name);
using (var message = await client.PostAsync("https://www.yammer.com/api/v1/pending_attachments", content))
{
if (message.IsSuccessStatusCode)
{
var result = await message.Content.ReadAsStringAsync();
pa = Newtonsoft.Json.JsonConvert.DeserializeObject<PendingAttachment>(result);
return pa;
}
}
}
}
return null;
}
var FilePath = #"D:\Workspace\Lorem ipsum dolor sit amet.docx";
var pa = await Upload(FilePath);
MessageParam message = new MessageParam()
{
body = "posting attachment",
group_id = XXXXXXX,
pending_attachment1 = pa.id
};
var result = await CreateMessageAsync(message);
PendingAttachment Class and its property class
public class PendingAttachment
{
public int id { get; set; }
public int network_id { get; set; }
public string url { get; set; }
public string web_url { get; set; }
public string type { get; set; }
public string name { get; set; }
public string original_name { get; set; }
public string full_name { get; set; }
public string description { get; set; }
public string content_type { get; set; }
public string content_class { get; set; }
public string created_at { get; set; }
public int owner_id { get; set; }
public bool official { get; set; }
public string small_icon_url { get; set; }
public string large_icon_url { get; set; }
public string download_url { get; set; }
public string thumbnail_url { get; set; }
public string preview_url { get; set; }
public string large_preview_url { get; set; }
public int size { get; set; }
public string owner_type { get; set; }
public string last_uploaded_at { get; set; }
public int last_uploaded_by_id { get; set; }
public string last_uploaded_by_type { get; set; }
public object uuid { get; set; }
public object transcoded { get; set; }
public object streaming_url { get; set; }
public string path { get; set; }
public int y_id { get; set; }
public string overlay_url { get; set; }
public string privacy { get; set; }
public object group_id { get; set; }
public bool is_pending { get; set; }
public int height { get; set; }
public int width { get; set; }
public string scaled_url { get; set; }
public Image image { get; set; }
public int latest_version_id { get; set; }
public string status { get; set; }
public Latest_Version latest_version { get; set; }
public Stats stats { get; set; }
public string _OriginalFileName { get; set; }
}
public class Image
{
public string url { get; set; }
public int size { get; set; }
public string thumbnail_url { get; set; }
}
public class Latest_Version
{
public int id { get; set; }
public int file_id { get; set; }
public string content_type { get; set; }
public int size { get; set; }
public int uploader_id { get; set; }
public string created_at { get; set; }
public string path { get; set; }
public string download_url { get; set; }
public string thumbnail_url { get; set; }
public string preview_url { get; set; }
public string large_preview_url { get; set; }
public string post_processed_id { get; set; }
public object streaming_url { get; set; }
public string revert_url { get; set; }
public int height { get; set; }
public int width { get; set; }
public string scaled_url { get; set; }
public string thumbnail_path { get; set; }
public string preview_path { get; set; }
public string large_preview_path { get; set; }
public string status { get; set; }
}
public class Stats
{
public int following { get; set; }
public int followers { get; set; }
public int updates { get; set; }
public object first_reply_id { get; set; }
public object first_reply_at { get; set; }
public int latest_reply_id { get; set; }
public string latest_reply_at { get; set; }
public int shares { get; set; }
}