Async calls in c# - c#-4.0

Question

When I execute the code I developed to call an Async method of the linq2Twitter, I am getting a System.Aggregate Exception, the code is below:
static async Task<List<myTwitterStatus>> getRetweets(ulong tweetID, TwitterContext twitterCtx)
{
List<myTwitterStatus> reTweets = new List<myTwitterStatus>();
var publicTweets =
await
(from tweet in twitterCtx.Status
where tweet.Type == StatusType.Retweets &&
tweet.ID == tweetID
select tweet)
.ToListAsync();
if (publicTweets != null)
publicTweets.ForEach(tweet =>
{
if (tweet != null && tweet.User != null)
{
myTwitterStatus tempStatus = new myTwitterStatus();
tempStatus.Country = tweet.Place.Country;
tempStatus.createdAt = tweet.CreatedAt;
tempStatus.FavoriteCount = long.Parse(tweet.FavoriteCount.ToString());
tempStatus.ID = tweet.ID;
tempStatus.isTruncated = tweet.Truncated;
tempStatus.Lang = tweet.Lang;
tempStatus.MaxID = tweet.MaxID;
tempStatus.PlaceFullname = tweet.Place.FullName;
tempStatus.RetweetCount = tweet.RetweetCount;
tempStatus.ScreenName = tweet.ScreenName;
tempStatus.Text = tweet.Text;
tempStatus.UserFriends = tweet.User.FriendsCount;
tempStatus.UserCreated = tweet.User.CreatedAt;
tempStatus.UserFollowers = tweet.User.FollowersCount;
tempStatus.UserFavorities = tweet.User.FavoritesCount;
tempStatus.UserFriends = tweet.User.FriendsCount;
tempStatus.UserLocation = tweet.User.Location;
tempStatus.UserName = tweet.User.Name;
tempStatus.UserTweetCount = tweet.User.StatusesCount;
reTweets.Add(tempStatus);
}
});
return reTweets;
}
The issue is when I called the method
var authorizer = new SingleUserAuthorizer
{
CredentialStore = new InMemoryCredentialStore
{
ConsumerKey = SM.Default.Consumer_key2.ToString(),
ConsumerSecret = SM.Default.Consumer_secret2.ToString(),
OAuthToken = SM.Default.Access_token2.ToString(),
OAuthTokenSecret = SM.Default.Access_secret2.ToString()
}
};
TwitterContext twitterCtx = new TwitterContext(authorizer);
Task<List<myTwitterStatus>> task = Task<List<myTwitterStatus>>.Factory.StartNew(() => getRetweets(ulong.Parse(tweet.StringId), twitterCtx).Result);
task.Wait();
List<myTwitterStatus> tempList = task.Result.ToList<myTwitterStatus>();
foreach (var ret in tempList)
{
un = file.RemoveSpecialCharacters(ret.UserName);
sn = file.RemoveSpecialCharacters(ret.ScreenName);
tweets.AppendLine(account + "," + getWE(ret.createdAt) + "," + Text + "," + un + "," + sn + "," + ret.createdAt + "," +
file.RemoveSpecialCharacters(ret.UserLocation) + ",,,1,," + ret.UserTweetCount + "," +
ret.RetweetCount + "," + ret.FavoriteCount + "," + ret.UserFollowers);
I would appreciate any kind of assistance about it, I have no idea how to solve it.

Answer 1

Can you add a try/catch so see what the inner exception is.
try
{
//Perform your operation here
}
catch (AggregateException aex)
{
//Dive into inner exception
}

Answer 2

Thanks to all for the help, I activate the breakpoints for the specific exception and an additional validation was added, the issue was not in the async process, it was because it was trying to handle a null as an string, to hendle this error this line was modified sn = file.RemoveSpecialCharacters(ret.ScreenName ?? string.Empty);
The full code is below:
private void getRetweets(TwitterStatus tweet)
{
Text = file.RemoveSpecialCharacters(tweet.Text);
tweetID = tweet.StringId;
#region Get retweets
RetweetsOptions retOpt = new RetweetsOptions();
if (int.Parse(tweet.RetweetCountString.ToString()) > 1)
retOpt.Count = int.Parse(tweet.RetweetCountString.ToString()) + 1;
else
retOpt.Count = 1;
String errorText = "";
DateTime fromDate, toDate;
if (radDate.Checked == true)
{
fromDate = dtpFrom.Value;
toDate = dtpTo.Value;
}
else
{
fromDate = tweet.CreatedDate;
toDate = DateTime.Now;
}
TwitterResponse<TwitterStatusCollection> retweet = null;
if (int.Parse(tweet.RetweetCountString.ToString()) > 100)
{
var authorizer = new SingleUserAuthorizer
{
CredentialStore = new InMemoryCredentialStore
{
ConsumerKey = SM.Default.Consumer_key2.ToString(),
ConsumerSecret = SM.Default.Consumer_secret2.ToString(),
OAuthToken = SM.Default.Access_token2.ToString(),
OAuthTokenSecret = SM.Default.Access_secret2.ToString()
}
};
TwitterContext twitterCtx = new TwitterContext(authorizer);
//HELPER: https://www.youtube.com/watch?v=IONqMWGn9-w
try
{
Task<List<myTwitterStatus>> task = null;
Parallel.Invoke(
() =>
{
task = getRetweets(ulong.Parse(tweet.StringId), twitterCtx);
while (!task.IsCompleted)
{
Thread.Sleep(250);
}
});
List<myTwitterStatus> tempList = task.Result.ToList<myTwitterStatus>();
foreach (var ret in tempList)
{
un = file.RemoveSpecialCharacters(ret.UserName);
sn = file.RemoveSpecialCharacters(ret.ScreenName ?? string.Empty);
tweets.AppendLine(account + "," + getWE(ret.createdAt) + "," + Text + "," + un + "," + sn + "," + ret.createdAt + "," +
file.RemoveSpecialCharacters(ret.UserLocation) + ",,,1,," + ret.UserTweetCount + "," +
ret.RetweetCount + "," + ret.FavoriteCount + "," + ret.UserFollowers);
}
}catch(Exception ex){
Console.WriteLine("Error: " + ex.Message+ Environment.NewLine + ex.StackTrace);
}
return;
}
else
retweet= TwitterStatus.Retweets(tokensRet, Decimal.Parse(tweet.Id.ToString()), retOpt);
if (retweet.Result.ToString() == "Success" && retweet.ResponseObject.Count > 0 && retweet!=null)
{
int retPages = int.Parse(tweet.RetweetCountString.ToString()) + 1 / 20;
for (int page = 0; page <= retPages; page++)
{
try
{
//List<TwitterStatus> retList = new List<TwitterStatus>(retweet.ResponseObject.Page = page);
retweet.ResponseObject.Page = page;
List<TwitterStatus> retList = retweet.ResponseObject.ToList<TwitterStatus>();
foreach (var ret in retList)
{
try
{
if (ret.CreatedDate.CompareTo(fromDate) >= 0 && ret.CreatedDate.CompareTo(toDate) <= 0)
{
#region Get UN Sync
getUN(ret, ref un, ref sn);
#endregion
tweets.AppendLine(account + "," + getWE(ret.CreatedDate) + "," + Text + "," + un + "," + sn + "," + ret.CreatedDate + "," +
file.RemoveSpecialCharacters(ret.User.Location.ToString()) + ",,,1,," + ret.User.NumberOfStatuses.ToString() + "," +
ret.RetweetCount + "," + ret.User.NumberOfFavorites.ToString() + "," + ret.User.NumberOfFollowers.ToString());
}
else if (tweet.CreatedDate.CompareTo(toDate) <= 0)//if the tweet's created date is lower than the from's date, exits the loop
break;
}
catch (NullReferenceException ex)
{
errorText = ex.Source + Environment.NewLine + ex.StackTrace;
continue;
}
}
}
catch (Exception ex)
{
errorText = ex.Source + Environment.NewLine + ex.StackTrace;
//MessageBox.Show(ex.Message + Environment.NewLine + "Rate Limit was reached!" + Environment.NewLine +
// "Wait an hour or try a shorter date range", "Rate Limit Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
else if (error == false && retweet.Result.ToString() != "Success")
{
errorText = retweet.Result.ToString();
MessageBox.Show("Retweets: Something went wrong!" + Environment.NewLine + errorText, "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
error = true;
}
#endregion
}