これはうまくいきます
var attachment = new JsonObject();
var media = new[]{
new{
type="jpeg",
src = filePath,
title= "title",
artist= "art",
album= "album"
}
};
//var mediaArray = new JsonArray { media };
attachment.Add("name", "sfs");
attachment.Add("href", "http://www.google.com");
attachment.Add("caption", " asdas");
attachment.Add("description", description);
attachment.Add("target_id", "1231231");
attachment.Add("media", media);
var sb = new StringBuilder("https://api.facebook.com/method/stream.publish?");
sb.Append("message="); sb.Append(description + "&");
sb.Append("attachment=");
sb.Append(attachment);
sb.Append("&access_token=");
sb.Append(accessToken);
var req = WebRequest.Create(sb.ToString());
req.GetResponse();