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How to send information from a class using a backgroundworker, back to the mainform

Hi,
I'm trying to write a UDP-client that listens to a port, and then display the incoming data in a textbox.
I have written a class; UDP_Receive() that starts a backgroundworker that listens to a specified port and receives the data. The code is based on this question; C# .Net receiving UDp packets in separater thread and application exit
I think I have solved the issues with the blocking .receive() by following the accepted answer in this question; How can I safely terminate UdpClient.receive() in case of timeout?
My question is how do I get the data I receive in the backgroundworkerthread (that I created in my class) back to the mainthread, so that I can display it in a textbox?
I thought of using Invoke, but I don't have any references to the textbox in my class.
textBox_UdpPositionInData.Invoke(new EventHandler(delegate
{
textBox_UdpPositionInData.Text = receivedData;
}));
I found a very similar question about a tcp-server, but I can't see how to apply that solution here Send data from a background thread to the main thread
Any thoughts or suggestions are of course much appreciated!
Many Thanks!
internal class UDP_Receive
{
private int _portToListen = 2003;
private volatile bool listening;
BackgroundWorker _backgroundWorker;
//Constructor
public UDP_Receive()
{
Debug.WriteLine("Constructor: UDP_Receive");
this.listening = false;
}
public void StartListener()
{
if ( (_backgroundWorker==null) || (!_backgroundWorker.IsBusy))
{
_backgroundWorker = new BackgroundWorker();
_backgroundWorker.DoWork += listenForUDPPackages_DoWork;
_backgroundWorker.RunWorkerCompleted +=listenForUDPPackages_RunWorkerCompleted;
_backgroundWorker.WorkerSupportsCancellation = true;
_backgroundWorker.RunWorkerAsync();
Debug.WriteLine("Creates a new thread: " + _backgroundWorker.ToString() );
// We are listening
this.listening = true;
}
}
public void StopListener()
{
// The user cancelled the UDP Port listening
this.listening = false;
// Cancel the backgroundworker
_backgroundWorker.CancelAsync();
// Debug
Debug.WriteLine("Stops current thread: " + _backgroundWorker.ToString());
}
public bool IsListening
{
get { return this.listening; }
}
public int PortToListen
{
get { return this._portToListen; }
set { this._portToListen = value; }
}
private void listenForUDPPackages_DoWork(object sender, DoWorkEventArgs ev)
{
UdpClient? listener = null;
try
{
listener = new UdpClient(_portToListen);
}
catch (SocketException)
{
//do nothing
}
if (listener != null)
{
IPEndPoint groupEP = new IPEndPoint(IPAddress.Any, _portToListen);
try
{
while (this.listening)
{
Debug.WriteLine("Waiting for UDP broadcast to port " + _portToListen);
byte[] receivedBytes = new byte[1024];
string receivedData;
bool timeTracker = TrackFunction(TimeSpan.FromSeconds(2), () =>
{
receivedBytes = listener.Receive(ref groupEP);
});
Debug.WriteLine("Timetracker result: " + timeTracker.ToString());
if (receivedBytes == null || receivedBytes.Length == 0)
{
// We did not recieve any data
Debug.WriteLine("No data received befor Time out ");
}
else
{
// We managed to receive some data!
// No we want to process the data and then send the result to the Thread that initiated the class.
receivedData = Encoding.Default.GetString(receivedBytes);
Debug.WriteLine("Data received: " + receivedData);
}
}
catch (Exception e)
{
Debug.WriteLine("Exception: " + e.ToString());
}
finally
{
listener.Close();
Debug.WriteLine("Finally: Done listening for UDP broadcast");
}
}
else
{
Debug.WriteLine("Error: UdpClient(_portToListen) returned null");
}
}
private void listenForUDPPackages_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e == null || e.Result == null)
{
Debug.WriteLine("listenForUDPPackages_RunWorkerCompleted e = null");
}
else
{
if (e.Cancelled)
{
Debug.WriteLine("Operation was canceled");
}
else if (e.Error != null)
{
Debug.WriteLine("Error: " + e.Error.Message);
}
else
{
Debug.WriteLine("Result: " + e.Result.ToString());
}
}
}
private static bool TrackFunction(TimeSpan timeSpan, Action codeBlock)
{
try
{
Task task = Task.Factory.StartNew(() => codeBlock());
task.Wait(timeSpan);
return task.IsCompleted;
}
catch (AggregateException ae)
{
throw ae.InnerExceptions[0];
}
}
}

You can write this kind of code to keep the UI separate from the UDP_Receive class:
internal class UDP_Receive
{
private Action<string> _invoke;
public UDP_Receive(Action<string> invoke)
{
_invoke = invoke;
}
public void Foo()
{
_invoke("Hello");
}
}
When you declare the class you then do it like this:
var ur = new UDP_Receive(t => textBox.Invoke(() => textBox.Text = t));
Now it's just a matter of calling ur.Foo() (in my example) to update the UI.

why Invoke doesn't work in another class

I would monitor data received on a Serial port with my pc and a Arduino.
On the arduino, the sketch send thorugt the USB the string "aabb" evry 300ms.
With pc I want listen, and in real time print the string in a control (Textbox). To do that, I create a new thread which listen in a Loop what arrives in Serial port, and when it happens it write by a Invoke the string in textbox. The procedures works if I deploy in the form's class but if I use a external class it doesn't. To explain better the matter, I paste the code of the class
class SerialPortManager
{
public SerialPort Serial = new SerialPort();
private Thread thr;
private string Log;
public TextBox textLog;
public string LastString;
public bool thrIsAlive;
[Browsable(false)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
[EditorBrowsable(EditorBrowsableState.Advanced)]
[IODescriptionAttribute("ControlInvokeRequiredDescr")]
public bool InvokeRequired { get; private set; }
//DISPOSE
public void Dispose()
{
this.Dispose();
}
//SET Textobox LOG
public void SetLogTxtB (TextBox txt)
{
textLog = txt;
}
//PORTE DISPONIBILI
public string[] Available_Ports()
{
return SerialPort.GetPortNames();
}
//COSTRUTTORI
public SerialPortManager(string portname, int baudrate,bool InitializeConn)
{
Serial.BaudRate = baudrate;
Serial.PortName = portname;
if (InitializeConn == true) Serial.Open();
}
public SerialPortManager()
{
}
//SETTA I PARAMETRI E INIZIALIZZA LA CONNESSIONE
public void SetConnectionParam(string portname, int baudrate, bool initializeConn)
{
Serial.Close();
Serial.Dispose();
Serial = new SerialPort();
Serial.BaudRate = baudrate;
Serial.PortName = portname;
if (initializeConn == true) Serial.Open();
}
//ASYNC LISTENER
public void AsyncListener()
{
thrIsAlive = true;
thr = new Thread(ThreadReader);
thr.Start();
}
//PROCEDURA PER APPEND
public void AppendTextBox(string value)
{
if (InvokeRequired)
{
this.Invoke(new Action<string>(AppendTextBox), new object[] { value });
return;
}
textLog.Text += value;
}
private void Invoke(Action<string> action, params object[] v)
{
throw new NotImplementedException();
}
void ThreadReader()
{
while (thrIsAlive)
{
string temp = Serial.ReadLine();
LastString = temp;
Log += LastString + "\n";
AppendTextBox(LastString + "\n");
}
}
}
In the form I write three rows
SerialPortManager PortMan = new Driver_Arduin.SerialPortManager("COM3", 9600,true);
PortMan.SetLogTxtB(textBox1);
PortMan.AsyncListener();
If I try to run program it returns the error " cross-thread operation not allowed". Now, while I posting this ask, I decide to do a last try and change the method AppendTextBox to :
public void AppendTextBox(string value)
{
if (textLog.InvokeRequired)
{
try
{
textLog.Invoke(new Action<string>(AppendTextBox), new object[] { value });
return;
}
catch (ObjectDisposedException)
{
thrIsAlive = false;
}
}
textLog.Text += value;
}
And It Finally works. Now ascertained the power of Stackoverflow that solved the problem before posting, I would know why my code works. Thank you

In SerialPortManager you must use delegate instead windows control.
class SerialPortManager
{
public SerialPort Serial = new SerialPort();
private Thread thr;
private string Log;
//public TextBox textLog;
public Action<string> textLog;
.....
Crete in you form simply method:
public void SetTextBoxText(string value)
{
if (textBox1.InvokeRequired)
{
try
{
textBox1.Invoke(new Action<string>(AppendTextBox), new object[] { value });
return;
}
catch (ObjectDisposedException)
{
thrIsAlive = false;
}
}
textBox1.Text += value;
}
Set delegate to PortMan:
SerialPortManager PortMan = new Driver_Arduin.SerialPortManager("COM3", 9600,true);
PortMan.SetLogTxtB=new Action<string>(SetTextBoxText);
PortMan.AsyncListener();
If need output log to TextBox of PortMan call textLog delegate.
void ThreadReader()
{
while (thrIsAlive)
{
string temp = Serial.ReadLine();
LastString = temp;
Log += LastString + "\n";
//AppendTextBox(LastString + "\n");
textLog(LastString + "\n");
}
}

Apart from that your Invoke method in SerialPortManager should throw NotImplementedException the problem is that you define your own InvokeRequired/Invoke.
You need to use these methods provided by a WinForms control such that it knows whether your code is running inside the thread (UI thread) that created the control and how it can change context to this thread.
Actually it seems you may use your SerialPortManager but make use of InvokeRequired/Invoke of textLog like you're already doing in AppendTextBox.
BTW, if (initializeConn == true) is rather useless - if (initializeConn) is sufficient.

Show Form Message using non-Main UI Thread

I have a project that without usign any form/button or nothing like that, connects with a Websocket and using async methods receives some message(on a form created by myself) that is supposed to appear on the top-right corner of the screen.
But this message can appear from time to time (2 or 3 minutes) on the screen if the websocket doesn't say that it must stop. And this message can be big enough, that in order to make it look better I make my message appear in more than one form.
It causes an impression that it's a notification. So my class that connects with the websocket and receives the message async, calls another class using a thread that is a controller. The purpose of the controller is from time to time, show that message in various new form() notifications and obviously don't do it if the websocket doesn't return any message.
But when i call the form.show the program stops working.
I've looked around stackoverflow already, but the ideas that i've found didn't seem to work.
Some say that I should use invoke, but it kept giving error saying that
"Invoke or BeginInvoke cannot be called on a control until the window handle has been created", tried to solve like this: C# calling form.show() from another thread but it didn't work.
Some said that I should use .showDialog instead of .show, but it doesn't appear to be good, because it waits the window to be closed to terminate the method and as I said I need to open more than one notification at the same time.
Some said that the form was open with .show, but it was open for a very little period of time. But i couldn't notice if that was the case and even if it was i couldn't solve it. Well, what matter is that i'm stuck and i don't know what to do more.
Edited with Code:
//Main
Application.Run(new SocketService());
//SocketService class
public SocketService()
{
alerta = null;
while (true)
{
try
{
//Console.WriteLine("Nome do Usúario:" + Environment.UserName);
Thread.Sleep(2000);
Connect("ws://192.168.120.38:9091").Wait();
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
}
public static async Task Connect(string uri)
{
ClientWebSocket webSocket = null;
try
{
webSocket = new ClientWebSocket();
await webSocket.ConnectAsync(new Uri(uri), CancellationToken.None);
await Login(webSocket);
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (webSocket != null)
webSocket.Dispose();
lock (consoleLock)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("WebSocket closed.");
Console.ResetColor();
}
}
}
private static async Task Login(ClientWebSocket webSocket)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(encoder.GetBytes( "{\"event\":\"loginBrowser\",\"data\":{\"login\":\"000000003077\",\"data\":\"1\"}}"));
await webSocket.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);
if (webSocket.State == WebSocketState.Open)
{
if (ShowMessage.created != true)
{
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
new Thread(ThreadProc).Start();
}
await Receive(webSocket);
}
}
private static async Task Receive(ClientWebSocket webSocket)
{
while (webSocket.State == WebSocketState.Open)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(new Byte[256]);
var result = await webSocket.ReceiveAsync(buffer, CancellationToken.None);
if (result.MessageType == WebSocketMessageType.Close)
{
await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
}
else
{
if (result.EndOfMessage)
{
message += encoder.GetString(buffer.ToArray());
SendMessage(message);
}
else
{
message += encoder.GetString(buffer.ToArray());
}
}
}
}
public static void ShowFormFromAnotherThread(string text)
{
_sync.Post(SendOrPostCallback, text);
}
private static void SendOrPostCallback(object state)
{
var form = new Notification();
form.Text = (string)state;
form.Show();
}
private static void ThreadProc()
{
while (true)
{
Thread.Sleep(2000); // wait imitation
ShowFormFromAnotherThread("HI");
}
}
/*Notification is my form and depending on where I put this part:
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
new Thread(ThreadProc).Start();
Or i doesn't call login or doesn't enter receive() method or the best case It receives the information
calls the threadProc and the ShowFormFromAnotherThread but doesn't enter SednOrPostCallBack*/

using System.Threading;
using System.Windows.Forms;
namespace ConsoleThreadSync
{
internal class Program
{
private static void Main(string[] args)
{
Application.Run(new App());
}
}
public class App : ApplicationContext
{
private readonly SynchronizationContext _sync;
public App()
{
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
new Thread(ThreadProc).Start();
}
public void ShowFormFromAnotherThread(string text)
{
_sync.Post(SendOrPostCallback, text);
}
private void SendOrPostCallback(object state)
{
var form = new Form1();
form.Text = (string)state;
form.Show();
}
private void ThreadProc()
{
while (true)
{
Thread.Sleep(2000); // wait imitation
ShowFormFromAnotherThread("HI");
}
}
}
}

Try to call this:
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
from a contructor SocketService() and not from async methods. This is an initialization code and it must call from main thread.

Okay, after reading a little bit more, the solution that kind worked out was this one, but the only way of using the
.show from the notifician is to use the Application.DoEvents and I've been warned from the sources that I've looked into
that this method should not be used, unless is the only option, because It can cause some problems with the Threads and other things.
So unless someone can give me another hint or clue about what to do, I have two options or use this method and try to fix some other bug
that It can cause or use the .showDialog because don't know why It works without any other problem, but to use .showDialog I've
to use another thread where I create and show the notification because if I don't do, the loop will stop at each iteration
in order to wait the .showDialog be closed. And as it isn't a problem I want to avoid using a lot of threads, because it can cause
another problem with the sync between them:
namespace ReiDoCSharp
{
class ShowMessage
{
private static RootObject alerta;
public static bool created;
private static int startPosition;
public static void setStartPosition(int start)
{
if (start < startPosition)
{
startPosition = start;
}
}
public RootObject getAlerta()
{
return ShowMessage.alerta;
}
public void setAlerta(RootObject root)
{
ShowMessage.alerta = root;
}
private static void DoWork()
{
while (true)
{
if (created != true)
{
created = true;
}
if (alerta != null)
{
string mensagem = "";
if ((alerta.data.Informacoes[1] != "") && (alerta.data.Informacoes[1] != null))
{
mensagem += alerta.data.Informacoes[1];
}
if ((alerta.data.Informacoes[0] != "") && (alerta.data.Informacoes[0] != null))
{
mensagem += alerta.data.Informacoes[0];
}
if (mensagem != "")
{
startPosition = 5;
string[] messages = mensagem.Split(new[] { "<br><br>" }, StringSplitOptions.None);
foreach (string message in messages)
{
Notification popup = new Notification();
popup.label1.Text = message;
popup.TopMost = true;
popup.Show();
Application.DoEvents();
/*Solution with the ShowDialog would be:
Task.Run(() => showNotification(message));
*/
}
}
}
Thread.Sleep(5000);
}
}
//Then I won't need to use Application.DoEvents, but would have to create more threads
private static Task showNotification(string message)
{
Notification popup = new Notification();
popup.label1.Text = message;
popup.TopMost = true;
popup.ShowDialog();
}
public static Task createPopupsAsync()
{
Task.Run(() => DoWork());
}
}
}
namespace ReiDoCSharp
{
class SocketService
{
private static object consoleLock = new object();
private const bool verbose = true;
private static readonly TimeSpan delay = TimeSpan.FromMilliseconds(3000);
private static UTF8Encoding encoder = new UTF8Encoding();
private static string message;
private static RootObject alerta;
public SocketService()
{
Begin();
}
public static void Begin()
{
alerta = null;
while (true)
{
try
{
Thread.Sleep(2000);
Connect("ws://192.168.120.38:9091").Wait();
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
}
public static async Task Connect(string uri)
{
ClientWebSocket webSocket = null;
try
{
webSocket = new ClientWebSocket();
await webSocket.ConnectAsync(new Uri(uri), CancellationToken.None);
await Login(webSocket);
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (webSocket != null)
webSocket.Dispose();
lock (consoleLock)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("WebSocket closed.");
Console.ResetColor();
}
}
}
private static async Task Login(ClientWebSocket webSocket)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(encoder.GetBytes("{\"event\":\"loginBrowser\",\"data\":{\"OPERADOR\":\"000000003077\",\"NRORG\":\"1\"}}"));
await webSocket.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);
if (webSocket.State == WebSocketState.Open)
{
Task.Factory.StartNew(() => ShowMessage.createPopupsAsync());
await Receive(webSocket);
}
}
private static async Task Receive(ClientWebSocket webSocket)
{
while (webSocket.State == WebSocketState.Open)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(new Byte[256]);
var result = await webSocket.ReceiveAsync(buffer, CancellationToken.None);
if (result.MessageType == WebSocketMessageType.Close)
{
await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
}
else
{
if (result.EndOfMessage)
{
message += encoder.GetString(buffer.ToArray());
SendMessage(message);
}
else
{
message += encoder.GetString(buffer.ToArray());
}
}
}
}
private static void LogStatus(bool receiving, byte[] buffer, int length, string assunto)
{
lock (consoleLock)
{
Console.ForegroundColor = receiving ? ConsoleColor.Green : ConsoleColor.Yellow;
if (verbose)
{
Console.WriteLine(encoder.GetString(buffer) + " " + assunto);
}
Console.ResetColor();
}
}
private static void SendMessage(string message)
{
message = message.Replace("event", "evento");
message = message.Replace("\0", "");
JavaScriptSerializer js = new JavaScriptSerializer();
RootObject mess = js.Deserialize<RootObject>(message);
if (mess.data.Informacoes[1] != "")
{
mess.data.Informacoes[1] += "<br>";
}
if (alerta == null)
{
alerta = mess;
}
else
{
if ((mess.data.Quantidade[0] != 0) && (mess.data.Quantidade == null))
{
if ((mess.data.Quantidade[0] == -1) && (mess.data.Informacoes[0] == ""))
{
alerta = null;
}
else
{
alerta = mess;
}
}
else if (mess.data.Quantidade[0] == 0)
{
alerta = null;
}
if ((mess.data.Quantidade[1] != 0) && (mess.data.Informacoes[1] != ""))
{
alerta = mess;
}
}
new ShowMessage().setAlerta(alerta);
message = "";
}
}
}

Gracefully quit a thread

I am developing a multithreaded application in C#, and I have now come to point where I have realised that my threads sometimes throw errors when I stop them via the .Abort(); .Join(); methods.
My current code for starting and stopping the thread is as follows:
public void StartLogging()
{
if (poller != null && poller.IsAlive)
{
poller.Abort();
poller.Join();
}
poller = new Thread(new ThreadStart(PollUSBDevice));
poller.IsBackground = true;
poller.Name = reference.VendorId.ToString() + ":" + reference.ProductId.ToString();
poller.Start();
IsLogging = true;
}
public void StopLogging()
{
if (poller != null && poller.IsAlive)
{
poller.Abort();
poller.Join();
IsLogging = false;
}
}
private void PollUSBDevice()
{
...Removed code - executes within milliseconds and I am not worried about stopping here.
ErrorCode ec = ErrorCode.None;
### THIS LOOPS FOR EVER OR UNTIL I CALL .Abort() ###
while (ec == ErrorCode.None && MyUsbDevice.IsOpen)
{
if (poller.ThreadState == System.Threading.ThreadState.AbortRequested)
{
reader.Abort();
reader.Dispose();
break;
}
else
{
byte[] readBuffer = new byte[8];
int bytesRead;
ec = reader.Read(readBuffer, 100, out bytesRead);
Application.Current.Dispatcher.BeginInvoke(
new OneArgDelegate(HandleData),
new object[] { readBuffer });
}
}
}
catch (Exception ex)
{
Do stuff....
}
finally
{
Close devices that are running in above while statement
}
}
I have tried other methods post here on Stackoverflow, however I just can't get my head around them (I'm newish to multithreading). Preferably, there would just be a bool switch on my parent object reference that I could check. IE:
public class Reference
{
public static bool gracefulStopRequested = false;
}
public void PollUSBDevice
{
while (ec == ErrorCode.None && !reference.gracefulStopRequested)
{
....
}
}
Can anyone point me to a good resource or give me a hint as to what search terms I should be searching for, or if you are in a really giving mood, possibly do a mockup of how you would handle this problem?

I would go for something like:
class Program
{
static void Main(string[] args)
{
Thread poller = new Thread(new ThreadStart(PollUSBDevice));
poller.Start();
Console.ReadLine();
StopPoller();
Console.WriteLine("Stopped");
Console.ReadLine();
}
public static void StopPoller()
{
_PollerStopRequested = true;
}
private static bool _PollerStopRequested = false;
private static void PollUSBDevice()
{
while (true && !_PollerStopRequested)
{
Console.WriteLine("running");
Thread.Sleep(500);
}
}
}
However this is just simulating a build in feature of C# BackgroundWorker, so you could also have a look at: http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker(v=vs.110).aspx

How to implement automatic printing with background threads?

I'm developing a program that receives some data and after processing I want to print it.It should be automatic printing.The data is added as records to printList queue.Then a thread is supposed to print them one by one.here's the code :
private void button4_Click(object sender, EventArgs e)
{
rwl.AcquireWriterLock(10);
try
{
if (automaticPrint == false)
{
automaticPrint = true;
_automaticPrintThread = new Thread(new ThreadStart(AutomaticPrintA4));
_automaticPrintThread.IsBackground = true;
_automaticPrintThread.Start();
}
else
{
automaticPrint = false;
if (_automaticPrintThread != null)
{
_automaticPrintThread.Join(1);
}
}
}
finally
{
rwl.ReleaseWriterLock();
}
}
private void AutomaticPrintA4()
{
try
{
this.AutomaticPrintA4Delegate();
}
catch (Exception e)
{
this._automaticPrintThread.Abort();
MessageBox.Show(e.StackTrace);
}
}
private void AutomaticPrintA4Delegate()
{
try
{
if (this.InvokeRequired)
this.Invoke(new MethodInvoker(AutomaticPrintA4Delegate));
else
{
rwl.AcquireReaderLock(100);
Telerik.Reporting.Processing.ReportProcessor rp = new Telerik.Reporting.Processing.ReportProcessor();
System.Drawing.Printing.PrinterSettings ps = new System.Drawing.Printing.PrinterSettings();
try
{
while (automaticPrint)
{
rwlprintlist.AcquireReaderLock(10);
try
{
if (Session.printList != null)
{
if (Session.printList.Count != 0)
{
if (Session.printList[0] != null)
{
rp.PrintReport(new Report(Session.printList[0]), ps);
LockCookie lc = rwlprintlist.UpgradeToWriterLock(10);
Session.printList.RemoveAt(0);
rwlprintlist.DowngradeFromWriterLock(ref lc);
}
}
else
{
Thread.Sleep(1000);
}
}
else
{
Thread.Sleep(1000);
}
}
finally
{
rwlprintlist.ReleaseReaderLock();
}
}
}
finally
{
rwl.ReleaseReaderLock();
}
}
}
catch (Exception e)
{
MessageBox.Show("Print : " + e.StackTrace + e.Message);
}
}
A button click controls automaticprint variable.
rwl controls access to automatic print and rwlprintlist controls access to printList.
but my main gui hangs whenever I start this thread.I don't know why?
P.S. any other design ideas would be appreciated.

In your background worker you call AutomaticPrintA4Delegate. This method switches to the UI thread with
if (this.InvokeRequired)
this.Invoke(new MethodInvoker(AutomaticPrintA4Delegate));
So the print out is running in the UI thread and that is the reason, why your UI is "hanging".