Facebook获取用户个人资料图片带ID

Question

我正在尝试使用Restsharp和C＃获取用户个人资料图片，但我在时间轴上为每个用户返回此错误：{"error":{"message":"(#210) Subject must be a page.","type":"OAuthException","code":210}}以下是我尝试获取图片的方式：

IEnumerable<Account> accounts = AccountStore.Create ().FindAccountsForService ("Facebook");
var enumerable = accounts as IList<Account> ?? accounts.ToList ();
Account facebook = enumerable.First ();
var facebookAccessToken = facebook.Properties ["access_token"].ToString ();
var request = new RestRequest (id + "/picture", Method.POST);
request.AddParameter ("access_token", facebookAccessToken);


var client = new RestClient ("https://graph.facebook.com/");
IRestResponse resp = client.Execute (request);
return resp.Content.ToString ();

我该如何解决这个问题？