Develop Reference

Multithread C# serialPort1_DataReceived event does not fire

I read/write data to serial port and I want to see reading on listbox right away. I created a new thread to send command to serial port. I keep the main thread empty, so, it can update the UI and also serial port event handler wont be interrupted with something else.(I am not sure is it right approach?)
The following code works with while (!dataRecieved) { Thread.Sleep(4000); } but does not works with while (!dataRecieved) { Thread.Sleep(100); }.
The problem is if I use 100ms sleep, serial port event handler fire only once and then program stops!(If I debug with breakpoint 100ms works because I create additional time when stepping into the code.) If I wait 4000ms the program works. Also, I check the time between sending data and receiving data from serial port is 200ms. So, 100ms is reasonable.
Here is the code:
public bool dataRecieved = false;
public Form1()
{
InitializeComponent();
}
public void AppendTextBox(string value)
{
this.Invoke((MethodInvoker)delegate { richTextBox1.Text += value + "\n";});
}
private void button1_Click(object sender, EventArgs e)
{
serialPort1.Open();
Thread testThread = new Thread(() => sendThread());
testThread.Start();
}
public void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
data = serialPort1.ReadLine();
dataRecieved = true;
}
public void sendThread()
{
for(int i = 0; i<10; i++)
{
serialPort1.WriteLine("AT" + i);
// Following line creates odd situation:
// if Thread.Sleep(100), I receive only first data, then program stops(serial port handler doesnt fire!).
// if Thread.Sleep(4000), I receive all data, successfuly works.
// But I do not want to wait 4000ms, because I receive answer from device in 200ms.
while (!dataRecieved) { Thread.Sleep(100); }
AppendTextBox("Received" + "AT" + i);
dataRecieved = false;
}
}
Where I am wrong? Can you please provide a solution?

I even didn't use a new Thead for write and read on SerialPort. You just need use update control in Invoke() is ok. Below is my update on richTextBox. You can change form richTextBox to your listbox.
public void update_RichTextBox(string message)
{
Invoke(new System.Action(() =>
{
txtReceivedData.Text += message;
txtReceivedData.Refresh();
txtReceivedData.SelectionStart = txtReceivedData.Text.Length;
txtReceivedData.ScrollToCaret();
}));
}
and the way to use above void:
if (ComPort.IsOpen)
{
ComPort.Write(_inputdata + "\r");
Form1._Form1.update_RichTextBox(_inputdata + "\r");
string _receviedData = ComPort.ReadExisting();
Form1._Form1.update_RichTextBox(respond);
ComPort.DiscardInBuffer();//delete all data in device's received buffer
ComPort.DiscardOutBuffer();// delete all data in transmit buffer
}
else
{
MessageBox.Show("haven't yet open COM port");
return "FLASE";
}

I use something I call "Cross Thread Linker"
#region Cross Thread Linker
public bool ControlInvokeRequired(Control c, Action a)
{
if (c.InvokeRequired) c.Invoke(new MethodInvoker(delegate { a(); }));
else return false;
return true;
}
void Update_RichTextBox(RichTextBox rtb, string Text)
{
if (ControlInvokeRequired(rtb, () => Update_RichTextBox(rtb, Text))) return;
rtb.AppendText(Text + Environment.NewLine);
}
#endregion
Then:
Update_RichTextBox(richTextBox1, "Text to append");

C# Invoking ListView not working (Background Thread)

Im working with WinForms.
I want to populate ListView from background thread but when im Invoking listview my program stops and shows an error. The error is "Cannot acces a disposed object. Object name is: ListView." And when i put this method
lvValidate.Invoke((Action)delegate
{
lvValidate.Items.Add(listitem);
});
in a try-catch block my program starts lagging. I dont know where is the problem,but my Invoke method is:
static class Intercept
{
internal static void Invoke(this Control control, Action action)
{
control.Invoke(action);
}
}
The error only showing when i close the form and open another form (in the same program). In the Form which contains the ListView the data is unreadable and it seems loads a thousands times.
Here's what my DoWork,ProgressChanged,RunWorkerCompleted event does.
private void bgwLoad_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
string commandText = "SELECT * FROM works";
MySqlCommand command = new MySqlCommand(commandText, connection);
MySqlDataAdapter da = new MySqlDataAdapter(command);
connection.Close();
connection.Open();
reader = command.ExecuteReader();
connection.Close();
DataTable dt = new DataTable();
da.Fill(dt);
for (int i = 0; i < dt.Rows.Count; i++)
{
DataRow dr = dt.Rows[i];
ListViewItem listitem = new ListViewItem(dr["ID"].ToString(), dr["Date"].ToString());
listitem.SubItems.Add(dr["Date"].ToString());
listitem.SubItems.Add(dr["Name"].ToString());
listitem.SubItems.Add(dr["WorkNumber"].ToString());
listitem.SubItems.Add(dr["WorkCode"].ToString());
listitem.SubItems.Add(dr["CoreThread"].ToString());
listitem.SubItems.Add(dr["Tech"].ToString());
listitem.SubItems.Add(dr["From"].ToString());
listitem.SubItems.Add(dr["To"].ToString());
listitem.SubItems.Add(dr["Validate"].ToString());
listitem.SubItems.Add(dr["Validate2"].ToString());
lvValidate.Items.Add(listitem);
}
}
private void bgwLoad_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e)
{
}
private void bgwLoad_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
picLoading.Visible = false;
}

Try the following:
Dispatcher.CurrentDispatcher.Invoke(() => {
lvValidate.Items.Add(listitem);
});
EDIT:
Or Try this:
public static void AddItem(ListItem listitem)
{
if (lvValidate.InvokeRequired)
{
AddItemDelegate d = new AddItemDelegate (AddItem);
lvValidate.Invoke(d, new object[] { listitem });
}
else
{
lvValidate.Invoke(new Action(() =>
{
lvValidate.Items.Add(listitem);
}));
}
}
delegate void AddItemDelegate(ListItem listitem);
Then call:
AddItem(listitem);

According to your comments, you are trying to retrieve Data from a DB using a DataAdapter, then handing out the Data piecemeal. This will not work for several reasons:
DataAdapter
The DataAdapter Classes all have in common that they only work, while the DBConnection is actively open. That is why you get "Cannot acces a disposed object". Because by the time you try to use it, it the connection is already Disposed. And disposing is not a thing you should ever delay. Or split up at all. Keep the using (that you hopefully got) right where it is, inside the DoWork().
For that reason you always have to copy the data of the DataAdapter into a non-Adapter collection. Really any old list would do. This will temporarily double the Memory load and might procude some stuff for the GC to clean up, but is really they only adviseable way.
Bulk Writes only in Completed
While you can theoretically hand out Partial Reads/process results via Progress Reporting, this is not adviseable to try. Writing a GUI has a massive overhead. The first and only time I did that, I ended up locking up my GUI thread with Write and Draw Operations. It looked like I had never done Multitasking. Updating a Progress bar is just about low cost enough to never really cause issues.
The default pattern is to only over write relevant amount of data after you got it all.
If you run into a exception or cancel, the pattern is to asume that all data is faulty and not have it on the UI.
I like to call the BackgroundWorker "Multitasking/-Threading Training Wheels". They teach you all those things. The firt part, by making the handing out akward. The second part, by actually throwing a Exception if you try to use the Result in invalid cases.
You propably retreive too much
Perhaps the most common mistake with DB's, is trying to retrieve a lot of data to then do processing or filtering in the Client. A common mistake, so avoid it.
There is a limit to how much data a User can process whatever you would define as 1 page. Never more then 100 Data Fields at once is my advice. If you got do Filtering, Pagination or the sort, always do it in the Query. Moving this stuff to the client moves a lot of unesessary data over the Network to then be slower at processing/Filtering then the DB would ever have been.
Example code
This actually is my first BGW Project. I updated it a bit over the years, but the bulk of it is still valid:
#region Primenumbers
private void btnPrimStart_Click(object sender, EventArgs e)
{
if (!bgwPrim.IsBusy)
{
//Prepare ProgressBar and Textbox
int temp = (int)nudPrim.Value;
pgbPrim.Maximum = temp;
tbPrim.Text = "";
//Start processing
bgwPrim.RunWorkerAsync(temp);
}
}
private void btnPrimCancel_Click(object sender, EventArgs e)
{
if (bgwPrim.IsBusy)
{
bgwPrim.CancelAsync();
}
}
private void bgwPrim_DoWork(object sender, DoWorkEventArgs e)
{
int highestToCheck = (int)e.Argument;
//Get a reference to the BackgroundWorker running this code
//for Progress Updates and Cancelation checking
BackgroundWorker thisWorker = (BackgroundWorker)sender;
//Create the list that stores the results and is returned by DoWork
List<int> Primes = new List<int>();
//Check all uneven numbers between 1 and whatever the user choose as upper limit
for(int PrimeCandidate=1; PrimeCandidate < highestToCheck; PrimeCandidate+=2)
{
//Report progress
thisWorker.ReportProgress(PrimeCandidate);
bool isNoPrime = false;
//Check if the Cancelation was requested during the last loop
if (thisWorker.CancellationPending)
{
//Tell the Backgroundworker you are canceling and exit the for-loop
e.Cancel = true;
break;
}
//Determin if this is a Prime Number
for (int j = 3; j < PrimeCandidate && !isNoPrime; j += 2)
{
if (PrimeCandidate % j == 0)
isNoPrime = true;
}
if (!isNoPrime)
Primes.Add(PrimeCandidate);
}
//Tell the progress bar you are finished
thisWorker.ReportProgress(highestToCheck);
//Save Return Value
e.Result = Primes.ToArray();
}
private void bgwPrim_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
pgbPrim.Value = e.ProgressPercentage;
}
private void bgwPrim_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
pgbPrim.Value = pgbPrim.Maximum;
this.Refresh();
if (!e.Cancelled && e.Error == null)
{
//Show the Result
int[] Primes = (int[])e.Result;
StringBuilder sbOutput = new StringBuilder();
foreach (int Prim in Primes)
{
sbOutput.Append(Prim.ToString() + Environment.NewLine);
}
tbPrim.Text = sbOutput.ToString();
}
else
{
tbPrim.Text = "Operation canceled by user or Exception";
}
}
#endregion

The code works but it lags when it works. It works with foreach and loop it

When the code is working so laggy it would be very good so that it is not laggy when it works.
How the code works:
It searches the computer for a file is then when it find it to change the file but if the file is running line will loop until it manages to do its job.
Main class
public Form1(string[] Args)
{
InitializeComponent();
backgroundWorker1.RunWorkerAsync();
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
Thread.Sleep(1000); // One second.Thread.Sleep(1000); // One second.
MessageBox.Show("Testing");
Fille mc = new Fille();
mc.Search();
}
Fille clss
private static ArrayList list2 = new ArrayList();
private static ArrayList listRemove = new ArrayList();
public void Search()
{
try
{
foreach (string file in Directory.EnumerateFiles(#"C:\Users\user\Downloads\MCFILE\trrtrt\", "*.exe", SearchOption.AllDirectories))
{
// Display file path.
if (SHA1Hash.GetSHA1Hash(file) == "1233456") // fake SHA1Hash
{
try
{
COPYWithReplace(#"C:\Users\user\Downloads\MCFILE\Fake2\Test.exe", file);
}
catch (IOException)
{
// log errors
if (list2.Count == 0)
{
list2.Add(file);
Thread thread = new Thread(new ThreadStart(Test2));
thread.Start();
}
else
{
Thread thread = new Thread(new ThreadStart(Test2));
thread.Abort();
list2.Add(file);
thread.Join();
}
}
}
}
}
catch (Exception ex)
{
// log errors
}
}
private void Test2()
{
if (list2.Count == 0)
{
}
else
{
foreach (string _item in list2)
{
try
{
//Run
COPYWithReplace(#"C:\Users\user\Downloads\MCFILE\Fake2\Test.exe", _item);
listRemove.Add(_item);
}
catch (IOException)
{
//error
}
}
foreach (var Remove in listRemove)
{
list2.Remove(Remove);
}
listRemove.Clear();
if (list2.Count == 0)
{
}
else
{
Thread thread = new Thread(new ThreadStart(Test2));
thread.Start();
}
}
}
I made a new thread because I found the problem. But now it's just that it lags.

I suspect the reason it's "lagging" is because you have the system in a very convoluted but rather processor intensive and I/O intensive loop. If a file fails the first test, your code starts a thread that tries it again. And if that fails then you start another thread to try it again, lather, rinse, repeat.
That's going to absolutely kill performance. You're basically doing this:
while (forever)
{
if I can overwrite the file
{
break;
}
}
Except if you have multiple files that you're trying to write, then you're doing that loop for every file. Concurrently. And you're not just using a loop. Instead, you're starting and stopping threads like nobody's business.
Yeah, that's going to slow down your computer.
A more reasonable way to do this would be with a thread to do the first check, and a timer that will limit how often you do the other checks. Communication is with a simple queue, because only one thread will be accessing it at a time.
Here's what I would recommend:
private static Queue<string> filesToCheck = new Queue<string>();
private System.Timers.Timer copyTimer;
public void Search()
{
try
{
foreach (string file in Directory.EnumerateFiles(#"C:\Users\user\Downloads\MCFILE\trrtrt\", "*.exe", SearchOption.AllDirectories))
{
// Display file path.
if (SHA1Hash.GetSHA1Hash(file) == "1233456") // fake SHA1Hash
{
if (!TryToCopy(file)) // See function below
{
filesToCheck.Enqueue(file);
}
}
}
// Checked all the files once.
// If there are any in the queue, start the timer.
if (filesToCheck.Count > 0)
{
copyTimer = new System.Timers.Timer(CopyTimerProc, null, 1000, Timeout.Infinite);
}
}
catch (Exception)
{
// do your error handling
}
}
private void CopyTimerProc(object state)
{
string filename = filesToCheck.Dequeue();
if (TryToCopy(filename))
{
// success. If the queue is empty, kill the timer.
if (filesToCheck.Count == 0)
{
copyTimer.Dispose();
}
}
else
{
// File still locked.
// Put it back on the queue and reset the timer.
filesToCheck.Enqueue(filename);
copyTimer.Change(1000, 0);
}
}
private bool TryToCopy(string filename)
{
try
{
COPYWithReplace(#"C:\Users\user\Downloads\MCFILE\Fake2\Test.exe", filename);
return true;
}
catch (IOException)
{
// log error
return false;
}
}
The timer is a one-shot that is reset after each time it ticks. The reason I did it this way is to prevent another tick coming along while the previous tick is still processing. After all, it takes time to copy a file.
There's no reason to do this with a bunch of threads. The file system can only do one thing at a time, anyway, and it's not like an extra second or two while you wait for a file to become available is going to hurt anything.

My program lock when I start the timer and I'm not sure why

I have created 2 programs. Both use timers with interval set to 250 milliseconds.
The problem is that my first program doesn't lock then I run it, and the second locks with out giving me ability to click stop button. By saying locks I mean that program runs do it's job until I stop it from VS.
I don't understand why I can't stop my first program while the basic same way work for other program. Any ideas?
Program that locks:
private void btnScan_Click(object sender, EventArgs e)
{
tmrInterval.Interval = (int)nudInterval.Value;
tmrInterval.Start();
}
private void ScanPort(IPAddress address, int port)
{
using (TcpClient client = new TcpClient())
{
IAsyncResult result = client.BeginConnect(address, port, null, null);
if (result.AsyncWaitHandle.WaitOne((int)nudTimeout.Value, false)) txtDisplay.AppendText("Port: " + port + " is open." + Environment.NewLine);
else txtDisplay.AppendText("Port: " + port + " is closed." + Environment.NewLine);
}
}
private void btnStop_Click(object sender, EventArgs e)
{
tmrInterval.Stop();
}
private void tmrInterval_Tick(object sender, EventArgs e)
{
ScanPort(IPAddress.Parse(txtIP.Text), currentPort);
currentPort++;
if (currentPort == nudTo.Value) tmrInterval.Stop();
}
Program that doesn't lock:
void tmrPingInterval_Tick(object sender, EventArgs e)
{
if (txtTo.Text == string.Empty) Ping(IPAddress.Parse(ip2str(startIP)));
else
{
if (currentIP >= endIP) tmrPingInterval.Stop();
Ping(IPAddress.Parse(ip2str(currentIP)));
currentIP++;
}
}
private void btnPing_Click(object sender, EventArgs e)
{
if (txtFrom.Text != string.Empty)
{
txtFrom.Enabled = false;
txtTo.Enabled = false;
txtDisplay.Text = string.Empty;
tsslPingCount.Text = string.Empty;
count = 0;
open = 0;
closed = 0;
tmrPingInterval.Interval = int.Parse(nudInterval.Value.ToString());
try
{
startIP = str2ip(txtFrom.Text);
if (txtTo.Text != string.Empty) endIP = str2ip(txtTo.Text);
currentIP = startIP;
tmrPingInterval.Start();
}
catch
{
MessageBox.Show("Input must be in IP format: 100.100.100.100", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
txtFrom.Enabled = true;
txtTo.Enabled = true;
}
}
else MessageBox.Show("IP field cannot be empty!", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
private void btnStop_Click(object sender, EventArgs e)
{
txtFrom.Enabled = true;
txtTo.Enabled = true;
tmrPingInterval.Stop();
}
private void Ping(IPAddress address)
{
Ping pingSender = new Ping();
PingOptions options = new PingOptions();
if (cbDontFragment.Checked) options.DontFragment = true;
else options.DontFragment = false;
string data = string.Empty;
int dataCounter = 0;
options.Ttl = (int)nudTTL.Value;
for (int i = 0; i < nudData.Value; i++)
{
dataCounter++;
if (dataCounter == 10) dataCounter = 0;
data += dataCounter.ToString();
}
byte[] buffer = Encoding.ASCII.GetBytes(data);
int timeout = 120;
try
{
PingReply reply = pingSender.Send(address, timeout, buffer, options);
if (reply.Status == IPStatus.Success)
{
}
else
{
}
}
catch (Exception ex)
{
txtDisplay.SelectedText += Environment.NewLine + ex.Message;
}
}

I'm going to make a guess here since we don't have enough information. I am guessing that tmrInterval in a System.Windows.Forms.Timer. If that is the case, the what's happening is that when the timer ticks, it is handed as a windows message (the same way that mouse clicks, keystrokes, and everything else that make your application appear 'not frozen' are handled).
In the first application, you are doing something that takes substantial time- opening a TCP port, then waiting for a (presumably) large number of milliseconds until the TCP connects or doesnt, then almost immediately doing it again the next time that the timer ticks. You are literally never giving the application a chance to respond to mouse clicks and keystrokes because the UI thread is busy trying to connect to some random ports somewhere.
In the second application, you are doing something relatively quick- just sending a ping somewhere. what you will probably see in the second application is that your application will 'stutter'- become unresponsive for just a second or less while it pings whatever other machine you pointed it at. It doesn't get hung because the UI thread isn't being given that much work to do.
To fix both of these, you should look into implementing a BackgroundWorker. Timers (of any sort) are not generally considered a good way to spawn background tasks in .NET.

About the first sample:
I guess from the context that the timer is a Windows.Forms.Timer. In the elapsed event you are executing a WaitOne(), and so effectively block the Messagepump.
As a possible solution, replace the Timer with a Threading.Timer to decouple the I/O from the main Thread.

C# Making a program finish processes before advancing

In C#, how do you make a program only process one thing at a time? I've been working on a patching system, and I think I have the coding all correct but can't test it because a lot of the functions are trying to process all at once when they need to be processing in an order. The program doesn't even let the display shown up before it starts trying to process everything. Because none of them return a value other then the main function all the functions are set to void. I thought about maybe using a return value inside of a loop to make sure the program is finished with that step first before moving on but it still leaves the problem of the program not even showing up until everything is done processing which its suppose to show the progress of everything. Any suggestions of tips?
Edit: I don't know what to post in the code, so im posting all the main functions:
public void DSP_Load(object sender, EventArgs e)
{
if (v1 >= v2)
{
File_Progress_Title.Text = "100%";
Update_Status.Text = "Divine Shadows is currently up to date.";
Application.DoEvents();
Process.Start("Divine Shadows.exe");
Close();
}
else
{
Update_Status.Text = "Checking For Updates...";
Application.DoEvents();
if (!Directory.Exists(tempFilePath))
{
Directory.CreateDirectory(tempFilePath);
}
using (SqlCon = new MySqlConnection(connString))
{
SqlCon.Open();
string command = "SELECT * FROM version where version > '" + v1 + "' ORDER BY version LIMIT 1";
MySqlCommand GetLatestVersion = new MySqlCommand(command, SqlCon);
using (MySqlDataReader DR = GetLatestVersion.ExecuteReader())
{
while(DR.Read())
{
do
{
string LatestVersion = Convert.ToString(DR.GetValue(1));
string WebURL = Convert.ToString(DR.GetValue(2));
update.DownloadFileAsync(new Uri(WebURL), tempFilePath + "patch" + LatestVersion + ".zip");
update.DownloadProgressChanged += new DownloadProgressChangedEventHandler(download);
update.DownloadFileCompleted += new AsyncCompletedEventHandler(extration);
Application.Restart();
}
while (v1 < v2);
Process.Start("Divine Shadows.exe");
Close();
}
}
}
}
}
public void download(object sender, DownloadProgressChangedEventArgs e)
{
if (v1 >= v2)
{
File_Progress_Title.Text = "100%";
Update_Status.Text = "Divine Shadows is currently up to date.";
Application.DoEvents();
Process.Start("Divine Shadows.exe");
Close();
}
else
{
Update_Status.Text = "Downloading Updates...";
Application.DoEvents();
File_Progress_Display.Value = e.ProgressPercentage;
File_Progress_Title.Text = Convert.ToString(e.ProgressPercentage) + "%";
}
}
public void extration(object sender, AsyncCompletedEventArgs e)
{
if (v1 >= v2)
{
File_Progress_Title.Text = "100%";
Update_Status.Text = "Divine Shadows is currently up to date.";
Application.DoEvents();
Process.Start("Divine Shadows.exe");
Close();
}
else
{
Update_Status.Text = "Installing Updates, Please Wait...";
Application.DoEvents();
UnzipFile(extactFile, extractLocation);
}
}
public static void UnzipFile(string extactFile, string extractLocation)
{
try
{
FastZip fastZip = new FastZip();
fastZip.CreateEmptyDirectories = false;
fastZip.ExtractZip(extactFile, extractLocation, FastZip.Overwrite.Always, null, null, null, false);
}
catch (Exception ex)
{
throw new Exception("Error unzipping file \"" + extactFile + "\"", ex);
}
File.Delete(extactFile);
}

Your problem is not WebClient() specific, its about how your application is working with threads.
In general, winforms applications have one GUI Thread. This thread is used to executed your methods and also updating the user interface. If you start a long term process, the gui thread gets locked till the operation is finished. Thats the reason why your display is not shown.
You can solve that problem by implementing the BackgroundWorker. On that website you can also find an example how to implement it. Let the BackgroundWorker do your patching process and use events inside the BackgroundWorker.RunWorkerAsync() method to update your GUI.

If you are using c#4 or newer you can use the Task Parallel Library to perform tasks asynchronously, thus leaving your UI response while thing are being downloaded. First of all you need a reference:
using System.Threading.Tasks;
And some code:
public void YourMainFunction()
{
var urls = new List<string>();
urls.Add("http://google.com");
urls.Add("http://yahoo.com");
foreach(var url in urls)
{
Task.Factory.StartNew<DownloadResult>(() =>
DownloadIt(url))
.ContinueWith(WorkDone, TaskScheduler.FromCurrentSynchronizationContext());
}
}
private class DownloadResult
{
public string Url {get; set;}
public string Result {get; set;}
}
private DownloadResult DownloadIt(string url)
{
var downloadResult = new DownloadResult{ Url = url };
var client = new WebClient();
downloadResult.Result = client.DownloadString(url);
return downloadResult;
}
private void WorkDone(Task<DownloadResult> task)
{
if(task.IsFaulted)
{
//An exception was thrown
MessageBox.Show(task.Exception.ToString());
return;
}
//Everything went well
var downloadResult = task.Result;
//Here you can update your UI to reflect progress.
MessageBox.Show(downloadResult.Result);
}