Develop Reference

Access token empty error when uploading large files to a ToDoTask using Graph Api

I am trying to attach large files to a ToDoTask using the Graph Api using the example in the docs for attaching large files for ToDoTask and the recommend class LargeFileUploadTask for uploading large files.
I have done this sucessfully before with attaching large files to emails and sending so i used that as base for the following method.
public async Task CreateTaskBigAttachments( string idList, string title, List<string> categories,
BodyType contentType, string content, Importance importance, bool isRemindOn, DateTime? dueTime, cAttachment[] attachments = null)
{
try
{
var _newTask = new TodoTask
{
Title = title,
Categories = categories,
Body = new ItemBody()
{
ContentType = contentType,
Content = content,
},
IsReminderOn = isRemindOn,
Importance = importance
};
if (dueTime.HasValue)
{
var _timeZone = TimeZoneInfo.Local;
_newTask.DueDateTime = DateTimeTimeZone.FromDateTime(dueTime.Value, _timeZone.StandardName);
}
var _task = await _graphServiceClient.Me.Todo.Lists[idList].Tasks.Request().AddAsync(_newTask);
//Add attachments
if (attachments != null)
{
if (attachments.Length > 0)
{
foreach (var _attachment in attachments)
{
var _attachmentContentSize = _attachment.ContentBytes.Length;
var _attachmentInfo = new AttachmentInfo
{
AttachmentType = AttachmentType.File,
Name = _attachment.FileName,
Size = _attachmentContentSize,
ContentType = _attachment.ContentType
};
var _uploadSession = await _graphServiceClient.Me
.Todo.Lists[idList].Tasks[_task.Id]
.Attachments.CreateUploadSession(_attachmentInfo).Request().PostAsync();
using (var _stream = new MemoryStream(_attachment.ContentBytes))
{
_stream.Position = 0;
LargeFileUploadTask<TaskFileAttachment> _largeFileUploadTask = new LargeFileUploadTask<TaskFileAttachment>(_uploadSession, _stream, MaxChunkSize);
try
{
await _largeFileUploadTask.UploadAsync();
}
catch (ServiceException errorGraph)
{
if (errorGraph.StatusCode == HttpStatusCode.InternalServerError || errorGraph.StatusCode == HttpStatusCode.BadGateway
|| errorGraph.StatusCode == HttpStatusCode.ServiceUnavailable || errorGraph.StatusCode == HttpStatusCode.GatewayTimeout)
{
Thread.Sleep(1000); //Wait time until next attempt
//Try again
await _largeFileUploadTask.ResumeAsync();
}
else
throw errorGraph;
}
}
}
}
}
}
catch (ServiceException errorGraph)
{
throw errorGraph;
}
catch (Exception ex)
{
throw ex;
}
}
Up to the point of creating the task everything goes well, it does create the task for the user and its properly shown in the user tasks list. Also, it does create an upload session properly.
The problem comes when i am trying to upload the large file in the UploadAsync instruction.
The following error happens.
Code: InvalidAuthenticationToken Message: Access token is empty.
But according to the LargeFileUploadTask doc , the client does not need to set Auth Headers.
param name="baseClient" To use for making upload requests. The client should not set Auth headers as upload urls do not need them.
Is not LargeFileUploadTask allowed to be used to upload large files to a ToDoTask?
If not then what is the proper way to upload large files to a ToDoTask using the Graph Api, can someone provide an example?

If you want, you can raise an issue for the same with the details here, so that they can have look: https://github.com/microsoftgraph/msgraph-sdk-dotnet-core/issues.

It seems like its a bug and they are working on it.
Temporarily I did this code to deal with the issue of the large files.
var _task = await _graphServiceClient.Me.Todo.Lists[idList].Tasks.Request().AddAsync(_newTask);
//Add attachments
if (attachments != null)
{
if (attachments.Length > 0)
{
foreach (var _attachment in attachments)
{
var _attachmentContentSize = _attachment.ContentBytes.Length;
var _attachmentInfo = new AttachmentInfo
{
AttachmentType = AttachmentType.File,
Name = _attachment.FileName,
Size = _attachmentContentSize,
ContentType = _attachment.ContentType
};
var _uploadSession = await _graphServiceClient.Me
.Todo.Lists[idList].Tasks[_task.Id]
.Attachments.CreateUploadSession(_attachmentInfo).Request().PostAsync();
// Get the upload URL and the next expected range from the response
string _uploadUrl = _uploadSession.UploadUrl;
using (var _stream = new MemoryStream(_attachment.ContentBytes))
{
_stream.Position = 0;
// Create a byte array to hold the contents of each chunk
byte[] _chunk = new byte[MaxChunkSize];
//Bytes to read
int _bytesRead = 0;
//Times the stream has been read
var _ind = 0;
while ((_bytesRead = _stream.Read(_chunk, 0, _chunk.Length)) > 0)
{
// Calculate the range of the current chunk
string _currentChunkRange = $"bytes {_ind * MaxChunkSize}-{_ind * MaxChunkSize + _bytesRead - 1}/{_stream.Length}";
//Despues deberiamos calcular el next expected range en caso de ocuparlo
// Create a ByteArrayContent object from the chunk
ByteArrayContent _byteArrayContent = new ByteArrayContent(_chunk, 0, _bytesRead);
// Set the header for the current chunk
_byteArrayContent.Headers.Add("Content-Range", _currentChunkRange);
_byteArrayContent.Headers.Add("Content-Type", _attachment.ContentType);
_byteArrayContent.Headers.Add("Content-Length", _bytesRead.ToString());
// Upload the chunk using the httpClient Request
var _client = new HttpClient();
var _requestMessage = new HttpRequestMessage()
{
RequestUri = new Uri(_uploadUrl + "/content"),
Method = HttpMethod.Put,
Headers =
{
{ "Authorization", bearerToken },
}
};
_requestMessage.Content = _byteArrayContent;
var _response = await _client.SendAsync(_requestMessage);
if (!_response.IsSuccessStatusCode)
throw new Exception("File attachment failed");
_ind++;
}
}
}
}
}

Async /Await call gets stuck in web API

We have a web API application which runs on .net4.6.1. We have tried several times to figure out the root cause where it is getting deadlock, but failed. Below is the code snippet. We are hitting this API endpoint every 1 minute. It will pick 300 transaction at a time for processing from the DB. We have observed that it get stuck when there are no files to process from the DB. Not sure though. It would be helpful if someone can help us.TIA
public class TaxEngineIntegratorController : ApiController
{
public async Task Get(int id)
{
try
{
await MainFileMethod();
}
catch (Exception Ex)
{
SerilogMethods.LogError(log, Ex, "Get");
}
}
public async Task MainFileMethod()
{
List<FileTransaction> lstFTtoLock = new List<FileTransaction>();
try
{
List<int> lstStatusIds = new List<int>();
lstStatusIds.Add(objStatusManager.GetStatusIdbyName(Status.ConversionToXmlSucceded));
lstStatusIds.Add(objStatusManager.GetStatusIdbyName(Status.Reprocess));
//Getting the serviceURL of TRTaxEngine
string seriviceURL = objConfigManager.GetConfigurationdbyKey(ConfigurationList.TRTaxEngineURL);
//Getting the output path for the file to be placed after processing
string outputfilePath = objConfigManager.GetConfigurationdbyKey(ConfigurationList.TRTaxOutputXMLFolder);
FileMasterManager objFileMasterManager = new FileMasterManager();
TRTaxXMLOperations objxmlresp = new TRTaxXMLOperations();
//Getting all the files list for proccessing from the DB
List<FileTransaction> lstFiletoProcess = await objTransManager.GetFileListforProcessingAsync(lstStatusIds, true);
lstFTtoLock = lstFiletoProcess;
if (lstFiletoProcess.Count == 0)
return;
if (lstFiletoProcess.Count > 0)
{
var tasks = new List<Task<string>>();
using (HttpClient httpClnt = new HttpClient())
{
httpClnt.Timeout = TimeSpan.FromMilliseconds(-1);
foreach (FileTransaction item in lstFiletoProcess)
{
TRXMLResponseModel objRespModel = new TRXMLResponseModel();
objRespModel.strxmlResponse = string.Empty;
string fullFileName = item.FilePath + item.ConvertedName;
objRespModel.outputFilename = outputfilePath + item.ConvertedName;
FileMaster fileMaster = objFileMasterManager.GetById(item.FileId);
//Proccessing the file and getting the output filedata
Task<string> t = objxmlresp.GetXMLResponse(seriviceURL, fullFileName, fileMaster.CountryId.GetValueOrDefault(), httpClnt, objFileOperation, objRespModel.outputFilename, item);
tasks.Add(t);
objRespModel.strxmlResponse = await t;
}
var result = await Task.WhenAll(tasks);
}
SerilogMethods.LogCustomException(log, "Http Client Destroyed in Tax Engine", "GetXMLResponse");
}
}
catch (Exception Ex)
{
if (lstFTtoLock != null && lstFTtoLock.Count > 0)
{
objTransManager.UpdateFileTransactionIsPickedtoFalse(lstFTtoLock);
}
throw Ex;
}
}
}
//Getting all the files list for proccessing from the DB
public async Task<List<FileTransaction>> GetFileListforProcessingAsync(List<int> lstStatusList, bool IsActive)
{
try
{
List<FileTransaction> lstFTList = new List<FileTransaction>();
using (SUTBACDEVContext db = new SUTBACDEVContext())
{
//DataTable dtFileTransactions = GetFileTransactionListAsync(lstStatusList, IsActive);
string connectionString = db.Database.GetDbConnection().ConnectionString;
var conn = new SqlConnection(connectionString);
string query = #"[SUTGITA].[GetFileListforProcessing]";
using (var sqlAdpt = new SqlDataAdapter(query, conn))
{
sqlAdpt.SelectCommand.CommandType = CommandType.StoredProcedure;
sqlAdpt.SelectCommand.Parameters.AddWithValue("#StatusId", string.Join(",", lstStatusList.Select(n => n.ToString()).ToArray()));
sqlAdpt.SelectCommand.Parameters.AddWithValue("#IsActive", IsActive);
sqlAdpt.SelectCommand.CommandTimeout = 60000;
DataTable dtFileTransactions = new DataTable();
sqlAdpt.Fill(dtFileTransactions);
if (dtFileTransactions != null && dtFileTransactions.Rows.Count > 0)
{
IEnumerable<long> ids = dtFileTransactions.AsEnumerable().ToList().Select(p => p["id"]).ToList().OfType<long>();
lstFTList = await db.FileTransaction.Include(x => x.File.Country).Where(x => ids.Contains(x.Id)).OrderBy(x => x.Id).ToListAsync();
}
}
}
return lstFTList;
}
catch (Exception ex)
{
throw ex;
}
}
public async Task<string> GetXMLResponse(string baseUrl, string fullFileName, int countryId, HttpClient client, FileOperations objFileOperation, string outputfilePath, FileTransaction item)
{
try
{
var fileData = new StringBuilder(objFileOperation.ReadFile(fullFileName));
using (HttpContent content = new StringContent(TransformToSOAPXml(fileData, countryId), Encoding.UTF8, "text/xml"))
{
using (HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, baseUrl))
{
request.Headers.Add("SOAPAction", "");
request.Content = content;
using (HttpResponseMessage response = await client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
{
response.EnsureSuccessStatusCode();
if (response.IsSuccessStatusCode)
{
using (Stream streamToReadFrom = await response.Content.ReadAsStreamAsync())
{
using (Stream streamToWriteTo = File.Open(outputfilePath, FileMode.Create))
{
await streamToReadFrom.CopyToAsync(streamToWriteTo);
}
}
var transactionEntry = new FileTransaction
{
FileId = item.FileId,
FilePath = outputfilePath,
ConvertedName = item.ConvertedName,
ActionedBy = Process.Process3,
TimeStamp = DateTime.UtcNow,
StatusId = objStatusManager.GetStatusIdbyName(Status.OutputXmlReceived),
IsActive = true,
CreatedBy = Others.Scheduler,
CreatedOn = DateTime.UtcNow,
ModifiedBy = Others.Scheduler,
ModifiedOn = DateTime.UtcNow
};
//Inserting the new record and Updating isActive filed of previous record in Tranasaction table(Calling updateDataonTRSuccess method of TRTaxXMLOperations class)
await updateDataonTRSuccessAsync(item, transactionEntry);
return "Success";
}
else
{
SerilogMethods.LogCustomException(log, "Error occured in Tax Engine", "GetXMLResponse");
//Log the SOAP response when the SOAP fails with an error message
if (response.Content != null)
{
throw new Exception(await response.Content.ReadAsStringAsync());
}
return null;
}
}
}
}
}
catch (Exception ex)
{
SerilogMethods.LogError(log, ex, "GetXMLResponse");
return null;
}
}
The following changes I have done to make it work to this specific method.
Removal of this line : objRespModel.strxmlResponse = await t;
and added configureawait(false) to this line :List lstFiletoProcess = await objTransManager.GetFileListforProcessingAsync(lstStatusIds, true).ConfigureAwait(false); Below is the working code
public async Task MainFileMethod()
{
List<FileTransaction> lstFTtoLock = new List<FileTransaction>();
try
{
List<int> lstStatusIds = new List<int>();
lstStatusIds.Add(objStatusManager.GetStatusIdbyName(Status.ConversionToXmlSucceded));
lstStatusIds.Add(objStatusManager.GetStatusIdbyName(Status.Reprocess));
//Getting the serviceURL of TRTaxEngine
string seriviceURL = objConfigManager.GetConfigurationdbyKey(ConfigurationList.TRTaxEngineURL);
//Getting the output path for the file to be placed after processing
string outputfilePath = objConfigManager.GetConfigurationdbyKey(ConfigurationList.TRTaxOutputXMLFolder);
FileMasterManager objFileMasterManager = new FileMasterManager();
TRTaxXMLOperations objxmlresp = new TRTaxXMLOperations();
//Getting all the files list for proccessing from the DB
List<FileTransaction> lstFiletoProcess = await objTransManager.GetFileListforProcessingAsync(lstStatusIds, true).ConfigureAwait(false);
lstFTtoLock = lstFiletoProcess;
if (lstFiletoProcess.Count == 0)
return;
if (lstFiletoProcess.Count > 0)
{
var tasks = new List<Task<string>>();
using (HttpClient httpClnt = new HttpClient())
{
httpClnt.Timeout = TimeSpan.FromMilliseconds(-1);
//Getting the files for processing
foreach (FileTransaction item in lstFiletoProcess)
{
TRXMLResponseModel objRespModel = new TRXMLResponseModel();
objRespModel.strxmlResponse = string.Empty;
string fullFileName = item.FilePath + item.ConvertedName;
objRespModel.outputFilename = outputfilePath + item.ConvertedName;
FileMaster fileMaster = objFileMasterManager.GetById(item.FileId);
//Proccessing the file and getting the output filedata
Task<string> t = objxmlresp.GetXMLResponse(seriviceURL, fullFileName, fileMaster.CountryId.GetValueOrDefault(), httpClnt, objFileOperation, objRespModel.outputFilename, item, objTransManager);
tasks.Add(t);
//objRespModel.strxmlResponse = await t;
}
var result = await Task.WhenAll(tasks);
}
}
}
catch (Exception Ex)
{
if (lstFTtoLock != null && lstFTtoLock.Count > 0)
{
objTransManager.UpdateFileTransactionIsPickedtoFalse(lstFTtoLock);
}
throw Ex;
}
}

My Recommendation:
The method "Get(int id)" is somewhat confusing. first, it takes "id" and does nothing with it. Also it return nothing so it is not a "Get" method. It is basically asking for all transactions with status "Status.ConversionToXmlSucceded" & "Status.Reprocess" and are active to be gotten and processed via the "objxmlresp.GetXMLResponse" method... You Dont Have To Await the "MainFileMethod();" in "Get(int id)" just return the task or return Ok(); and allow all the process to go on in the background. You can experiment with reducing the "sqlAdpt.SelectCommand.CommandTimeout = 60000;".

PuppeteerSharp Number of Chromium Instances

We use PuppeteerSharp to add the ability for users to download a PDF of our application. Unfortunately sometimes a huge number of Chromium processes are started and don't stop until a server restart.
Normally when a user downloads a pdf, 5 chromium processes start and those disappear when the download is finished.
This is our code:
private static LaunchOptions launchOptions = new LaunchOptions
{
ExecutablePath = chromepath,
Headless = true,
DefaultViewport = ViewPortOptions
};
public static void ExportPdf(string url, string location)
{
try
{
Task<string> task = Task.Run<string>(async () => await ExportPdfASync(url, location)));
task.Wait();
}
catch (Exception)
{
// Exception handling
}
}
public static async Task<string> ExportPdfASync(string url, string location)
{
using (var browser = await Puppeteer.LaunchAsync(LaunchOptions))
using (var page = await browser.NewPageAsync())
{
await page.SetViewportAsync(new ViewPortOptions() { Width = 1440, Height = 990, IsMobile = false, DeviceScaleFactor = 1.0 });
await page.SetJavaScriptEnabledAsync(true);
await page.GoToAsync(url);
await page.WaitForTimeoutAsync(1500);
var marginOptions = new MarginOptions()
{
Top = "10mm",
Left = "10mm",
Right = "10mm",
Bottom = "10mm"
};
var pdfOptions = new PdfOptions()
{
PrintBackground = true,
Format = PaperFormat.A4,
MarginOptions = marginOptions,
Landscape = landscape
};
await page.PdfAsync(location, pdfOptions);
}
return "";
}
The browser and page are in the using blocks so, even with an error those should be disposed.
Does anyone have a solution for this problem? We, and our servers would be very happy;)

Try this:
public static async Task<string> ExportPdfASync(string url, string location)
{
try
{
using (var browser = await Puppeteer.LaunchAsync(LaunchOptions))
using (var page = await browser.NewPageAsync())
{
await page.SetViewportAsync(new ViewPortOptions() { Width = 1440, Height = 990, IsMobile = false, DeviceScaleFactor = 1.0 });
await page.SetJavaScriptEnabledAsync(true);
await page.GoToAsync(url);
await page.WaitForTimeoutAsync(1500);
var marginOptions = new MarginOptions()
{
Top = "10mm",
Left = "10mm",
Right = "10mm",
Bottom = "10mm"
};
var pdfOptions = new PdfOptions()
{
PrintBackground = true,
Format = PaperFormat.A4,
MarginOptions = marginOptions,
Landscape = landscape
};
await page.PdfAsync(location, pdfOptions);
}
}
catch (Exception ex)
{
}
finally {
browser.CloseAsync();
page.CloseAsync();
}
return "";
}

Remembering log in credentials/permissions UWP/C# (Microsoft Cloud API)

I'm creating an app that access the Microsoft Cloud API to get health data. It uses OAuth to log in when you hit the Sign In Button
private void signinButton_Click(object sender, RoutedEventArgs e)
{
UriBuilder uri = new UriBuilder("https://login.live.com/oauth20_authorize.srf");
var query = new StringBuilder();
query.AppendFormat("redirect_uri={0}", Uri.EscapeDataString(RedirectUri));
query.AppendFormat("&client_id={0}", Uri.EscapeDataString(ClientId));
query.AppendFormat("&scope={0}", Uri.EscapeDataString(Scopes));
query.Append("&response_type=code");
uri.Query = query.ToString();
this.webView.Visibility = Visibility.Visible;
this.webView.Navigate(uri.Uri);
}
This brings up a webView with the page to log in using Microsoft credentials. Once completed, it leads to this:
private async void WebView_NavigationCompleted(WebView sender, WebViewNavigationCompletedEventArgs args)
{
//
// When the web view navigates to our redirect URI, extract the authorization code from
// the URI and use it to fetch our access token. If no authorization code is present,
// we're completing a sign-out flow.
//
if (args.Uri.LocalPath.StartsWith("/oauth20_desktop.srf", StringComparison.OrdinalIgnoreCase))
{
WwwFormUrlDecoder decoder = new WwwFormUrlDecoder(args.Uri.Query);
var code = decoder.FirstOrDefault((entry) => entry.Name.Equals("code", StringComparison.OrdinalIgnoreCase));
var error = decoder.FirstOrDefault((entry) => entry.Name.Equals("error", StringComparison.OrdinalIgnoreCase));
var errorDesc = decoder.FirstOrDefault((entry) => entry.Name.Equals("error_description", StringComparison.OrdinalIgnoreCase));
// Check the code to see if this is sign-in or sign-out
if (code != null)
{
// Hide the browser again, no matter what happened...
sender.Visibility = Visibility.Collapsed;
if (error != null)
{
this.responseText.Text = string.Format("{0}\r\n{1}", error.Value, errorDesc.Value);
return;
}
var tokenError = await this.GetToken(code.Value, false);
if (string.IsNullOrEmpty(tokenError))
{
this.responseText.Text = "Successful sign-in!";
this.signoutButton.IsEnabled = true;
this.signinButton.IsEnabled = false;
this.getProfileButton.IsEnabled = true;
this.getDevicesButton.IsEnabled = true;
this.getActivitiesButton.IsEnabled = true;
this.getDailySummaryButton.IsEnabled = true;
this.getHourlySummaryButton.IsEnabled = true;
}
else
{
this.responseText.Text = tokenError;
}
}
else
{
this.responseText.Text = "Successful sign-out!";
this.signoutButton.IsEnabled = false;
this.signinButton.IsEnabled = true;
this.getProfileButton.IsEnabled = false;
this.getDevicesButton.IsEnabled = false;
this.getActivitiesButton.IsEnabled = false;
this.getDailySummaryButton.IsEnabled = true;
this.getHourlySummaryButton.IsEnabled = false;
}
}
}
private async Task<string> GetToken(string code, bool isRefresh)
{
UriBuilder uri = new UriBuilder("https://login.live.com/oauth20_token.srf");
var query = new StringBuilder();
query.AppendFormat("redirect_uri={0}", Uri.EscapeDataString(RedirectUri));
query.AppendFormat("&client_id={0}", Uri.EscapeDataString(ClientId));
query.AppendFormat("&client_secret={0}", Uri.EscapeDataString(ClientSecret));
if (isRefresh)
{
query.AppendFormat("&refresh_token={0}", Uri.EscapeDataString(code));
query.Append("&grant_type=refresh_token");
}
else
{
query.AppendFormat("&code={0}", Uri.EscapeDataString(code));
query.Append("&grant_type=authorization_code");
}
uri.Query = query.ToString();
var request = WebRequest.Create(uri.Uri);
try
{
using (var response = await request.GetResponseAsync())
{
using (var stream = response.GetResponseStream())
{
using (var streamReader = new StreamReader(stream))
{
var responseString = streamReader.ReadToEnd();
var jsonResponse = JObject.Parse(responseString);
this.creds.AccessToken = (string)jsonResponse["access_token"];
this.creds.ExpiresIn = (long)jsonResponse["expires_in"];
this.creds.RefreshToken = (string)jsonResponse["refresh_token"];
string error = (string)jsonResponse["error"];
return error;
}
}
}
}
catch (Exception ex)
{
return ex.Message;
}
}
I don't want users to have to accept the permissions every time the app is launched. Is there a way to save credentials locally so that it automatically authenticates on launch? Thanks!

You can use
Windows.Storage.ApplicationData.Current.LocalSettings
This process good described by this answer Best Way to keep Settings for a WinRT App?
The code in link identity to UWP

Store the needed oauth parts in the credential locker API. Never store these kind of information in the normal settings API.
On start read the oauth information and use the refreshtoken to get a new access token.
More Information here.
https://msdn.microsoft.com/en-us/library/windows/apps/mt270189.aspx

How to create async http requests in a loop?

Yesterday I've found out how to create several async http requests without async/await. But today I need to do it in a loop: if some of responses don't satisfy some condition - I need to change a request for them and send these requests again. It may be repeated several times.
I've tried this code:
do
{
var loadingCoordinatesTasks = new List<Task<Terminal>>();
var totalCountOfTerminals = terminalPresetNode.ChildNodes.Count;
var uiTaskScheduler = TaskScheduler.FromCurrentSynchronizationContext();
foreach (var terminal in terminals.Except(_terminalsWithCoordinates))
{
var address = terminal.GetNextAddress();
var webRequest = (HttpWebRequest)WebRequest.Create(GeoCoder.GeoCodeUrl + address);
var webRequestTask = Task.Factory.FromAsync<WebResponse>(webRequest.BeginGetResponse,
webRequest.EndGetResponse,
terminal);
var parsingTask = webRequestTask.ContinueWith(antecedent =>
{
// Parse the response
});
loadingCoordinatesTasks.Add(parsingTask);
}
Task.Factory.ContinueWhenAll(loadingCoordinatesTasks.ToArray(), antecedents =>
{
foreach (var antecedent in antecedents)
{
var terminalWithCoordinates = antecedent.Result;
if (antecedent.Status == TaskStatus.RanToCompletion &&
!terminalWithCoordinates.Coordinates.AreUnknown)
{
_terminalsWithCoordinates.Add(terminalWithCoordinates);
_countOfProcessedTerminals++;
}
}
});
} while (_countOfProcessedTerminals < totalCountOfTerminals);
but is it possible to check the condition in while just after every single set of requests executed?

You can perform the check after increasing the count:
_countOfProcessedTerminals++;
if (_countOfProcessedTerminals >= totalCountOfTerminals)
{
break;
}
Is _countOfProcessedTerminals thread-safe though?

I manage to do it using recursion:
public void RunAgainFailedTasks(IEnumerable<Task<Terminal>> tasks)
{
Task.Factory.ContinueWhenAll(tasks.ToArray(), antecedents =>
{
var failedTasks = new List<Task<Terminal>>();
foreach (var antecedent in antecedents)
{
var terminal = antecedent.Result;
// Previous request was failed
if (terminal.Coordinates.AreUnknown)
{
string address;
try
{
address = terminal.GetNextAddress();
}
catch (FormatException) // No versions more
{
continue;
}
var getCoordinatesTask = CreateGetCoordinatesTask(terminal, address);
failedTasks.Add(getCoordinatesTask);
}
else
{
_terminalsWithCoordinates.Add(terminal);
}
}
if (failedTasks.Any())
{
RunAgainFailedTasks(failedTasks);
}
else
{
// Display a map
}
}, CancellationToken.None,
TaskContinuationOptions.None,
TaskScheduler.FromCurrentSynchronizationContext());
}
private Task<Terminal> CreateGetCoordinatesTask(Terminal terminal, string address)
{
var webRequest = (HttpWebRequest)WebRequest.Create(GeoCoder.GeoCodeUrl + address);
webRequest.KeepAlive = false;
webRequest.ProtocolVersion = HttpVersion.Version10;
var webRequestTask = Task.Factory.FromAsync<WebResponse>(webRequest.BeginGetResponse,
webRequest.EndGetResponse,
terminal);
var parsingTask = webRequestTask.ContinueWith(webReqTask =>
{
// Parse the response
});
return parsingTask;
}