Context: I am playing music through a media element, and using a slider to display the point in the song that it is at. That updating is done in a backgroundworker, for obvious reasons.
private void bgPlay_DoWork(object sender,DoWorkEventArgs e)
{
while (isMediaPlaying)
{
this.Dispatcher.Invoke((Action)(() =>
{
timelineSlider.Value = mediaElement1.Position.TotalMilliseconds;
}));
}
}
private void Library_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
try
{
mediaElement1.Stop();
isMediaPlaying = false;
mediaElement1.Source = new Uri(songData[Library.SelectedIndex].Location);
mediaElement1.Volume = (double)volumeSlider.Value;
mediaElement1.Play();
isMediaPlaying = true;
bgPlay.RunWorkerAsync();
}
catch(Exception ex) {
F.MessageBox.Show(ex.ToString());
}
}
When I play a song, then double click on a different one, the background worker is still looping and throws an exception because it reaches bgPlay.RunWorkerAsync(); before the previous instance has finished. I tried to use the isMediaPlaying bool to tell the backgroundworker when to exit the loop, but the main thread reaches bgPlay.RunWorkerAsync(); before it finishes.
You are suffering of a common mistake when one is barely starting to program with threading, a race condition
I'd advise rewriting the code like this:
private static String threadingLock = "";
private void bgPlay_DoWork(object sender,DoWorkEventArgs e)
{
while (true)
{
lock(threadingLock) {
if(!isMediaPlaying)
break;
}
this.Dispatcher.Invoke((Action)(() =>
{
timelineSlider.Value = mediaElement1.Position.TotalMilliseconds;
}));
}
}
private void Library_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
try
{
lock(threadingLock) {
isMediaPlaying = false;
}
mediaElement1.Stop();
mediaElement1.Source = new Uri(songData[Library.SelectedIndex].Location);
mediaElement1.Volume = (double)volumeSlider.Value;
mediaElement1.Play();
isMediaPlaying = true;
bgPlay.RunWorkerAsync();
}
catch(Exception ex) {
F.MessageBox.Show(ex.ToString());
}
}
As a friendly tip, add a Thread.sleep(200) before invoking the update on the slider. It will reduce cpu usage without affecting the functionality of your application.
Related
I have a class SendCountingInfo() and it will send a message to server every 5 minutes. The code inside this class are:
public void StartSendCountingInfo()
{
DoStartSendCountingInfo(300000);
}
private void DoStartSendCountingInfo(int iMiSecs)
{
_pingTimer = new System.Timers.Timer(iMiSecs);
_pingTimer.Elapsed += new System.Timers.ElapsedEventHandler(pingTimer_Elapsed);
_pingTimer.Start();
}
void pingTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
PingRemoteHost();
}
When I try to call it in the Windows Form class, it didn't work.
But, when I remove the timer and call PingRemoteHost() directly, it works. However, the form didn't load properly. It shows blank screen but the method PingRemoteHost() work.
Here is the code inside the windows form:
private void Layout_Load(object sender, EventArgs e)
{
tSystemChecker = new System.Timers.Timer(1000);
tSystemChecker.Elapsed += new System.Timers.ElapsedEventHandler(tSystemChecker_Elapsed);
tSystemChecker.Start();
this.WindowState = FormWindowState.Maximized;
}
void tSystemChecker_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
UIThreadWork(this, delegate
{
try
{
SuspendLayout();
DoCheckHardwareStatus();
DoCheckLanguage();
SendCountingInfo sci = new SendCountingInfo();
sci.StartSendCountingInfo();
}
catch (Exception exp)
{
System.Diagnostics.Debug.WriteLine(exp.Message);
System.Diagnostics.Debug.WriteLine(exp.Source);
System.Diagnostics.Debug.WriteLine(exp.StackTrace);
}
ResumeLayout(true);
});
}
Do you have any idea what's wrong?
Use a thread and see if the problem persist
using System.Threading;
//Put this where you want to start the first timer
Thread thread = new Thread(dowork =>
{
public void StartSendCountingInfo();
}
If you are updating the GUI use for your controls
guicontrol.BeginInvoke((MethodInvoker)delegate()
{
guicontrol.Text = "aa";
//etc
});
I've looked in many places for this but still haven't found a solution. What I'm trying to achieve is being able to use BackgroundWorker on a timed basis. Here's an example:
public Main()
{
isDbAvail = new BackgroundWorker();
isDbAvail.DoWork += isOnline;
isDbAvail.RunWorkerCompleted += rewriteOnlineStatus;
}
private void rewriteOnlineStatus(object sender, RunWorkerCompletedEventArgs e)
{
Subs.Connection connection = new Subs.Connection();
changeStatus(connection.isDbAvail());
}
private void isOnline(object sender, DoWorkEventArgs e)
{
while (true)
{
Console.WriteLine("Checking database connection");
System.Threading.Thread.Sleep(8000);
}
}
public void changeStatus(bool status)
{
if (status)
{
serverStatusVal.Text = "Connected";
serverStatusVal.ForeColor = System.Drawing.Color.DarkGreen;
}
else
{
serverStatusVal.Text = "Not connected";
serverStatusVal.ForeColor = System.Drawing.Color.Red;
}
}
What's happening here is that the isOnline method checks if there is a connection to the database (just an example) every 8 seconds and changes the text accordingly. What I've noticed though, is that the while loop inside the isOnline method causes the rewriteOnlineStatus method never to fire because it runs indefinitely. Is there another workaround to this?
I suggest you use BackgroundWorker.ReportProgress, and check connectivity in the background thread.
Something like this:
public Main()
{
isDbAvail = new BackgroundWorker();
isDbAvail.WorkerReportsProgress = true;
isDbAvail.DoWork += isOnline;
isDbAvail.ProgressChanged += rewriteOnlineStatus;
isDbAvail.RunWorkerAsync();
}
private void rewriteOnlineStatus(object sender, ProgressChangedEventArgs e)
{
changeStatus((bool)e.UserState);
}
private void isOnline(object sender, DoWorkEventArgs e)
{
while (true)
{
Console.WriteLine("Checking database connection");
Subs.Connection connection = new Subs.Connection();
isDbAvail.ReportProgress(0, connection.isDbAvail);
System.Threading.Thread.Sleep(8000);
}
}
Now the BackgroundWorker is doing the work, and reporting back to the UI thread via ProgressChanged.
private void button1_Click(object sender, EventArgs e)
{
button1.Enabled = false;
string IDs = ID.Text;
string[] eachIDs = Regex.Split(IDs, "\n");
foreach (var eachID in eachIDs)
{
getContent(eachID);
titleBox.Text = "Done";
}
}
private void getContent(string value)
{
label1.Text = value;
Thread.Sleep(5000);
}
I will give 4 id's as Input say "IDNUMBER01, IDNUMBER02, IDNUMBER03, IDNUMBER04" each in a new line in Rich Text Box.
The code splits them successfully. I want to show the Value of the ID being used in the current loop in a Label Text.
Problem with my code is it shows only the last ID which goes through the loop.
Probably your UI freezing and you can't see the changes.Try this, use async/await feature:
private async void button1_Click(object sender, EventArgs e)
{
button1.Enabled = false;
string IDs = ID.Text;
string[] eachIDs = Regex.Split(IDs, "\n");
foreach (var eachID in eachIDs)
{
await getContent(eachID);
titleBox.Text = "Done";
}
}
private async Task getContent(string value)
{
label1.Text = value;
await Task.Delay(5000);
}
This is because the UI is only Updated after the execution of this code, since they are executing in the same thread. You will need to open a thread, run this code, and call the dispatcher (or the Control.BeginInvoke if this app is Winforms) to update the UI.
EDIT
Try this:
private void button1_Click(object sender, EventArgs e)
{
button1.Enabled = false;
string IDs = ID.Text;
new System.Threading.Thread(() =>
{
string[] eachIDs = Regex.Split(IDs, "\n");
foreach (var eachID in eachIDs)
{
getContent(eachID);
titleBox.BeginInvoke((Action) delegate { titleBox.Text = "Done"; });
}
}).Start();
}
private void getContent(string value)
{
label1.BeginInvoke((Action) delegate { label1.Text = value; });
Thread.Sleep(5000);
}
In your example, you'd be better using a timer to display your value text. You're only seeing the last ID because the loop is executing very quickly, and using Thread.Sleep within the foreach isn't going to fly.
You could use Application.DoEvents() before the Thread.Sleep, but a timer is still your better option ... imho.
I have a C# winform application which needs to run multiple instance in synchronous way. The goal is to:
If the exe runs 3 times, it runs the first instance of the exe and the rest will wait until the first instance finishes the processing. Then, a next waiting exe intance will run and process and so on.
The exe will run one by one until it finish processing then the exe will terminates automatically af.
Any idea how to do this?
I already tried below:
private void CheckInstance()
{
bool _returnValue = true;
string _lockFile = string.Empty;
Random _rnd = new Random();
int _randomValue = _rnd.Next(100, 200);
int _rndmiliSec = 0;
_rndmiliSec = DateTime.Now.Millisecond * _rnd.Next(2, 6);
_lockFile = string.Concat(AppDomain.CurrentDomain.BaseDirectory, string.Format("/{0}", instanceFileName));
while (_returnValue)
{
_returnValue = File.Exists(_lockFile);
if (_returnValue)
{
Thread.Sleep(1000);
this.Hide();
}
else
{
try
{
Thread.Sleep((_rnd.Next(1000) + _rndmiliSec) + _rnd.Next(1000, 1500));
Functions.WriteLog(_lockFile, "Starting the process...");
Functions.WriteLog(_lockFile, string.Format("Start Time : {0}", paramPrintTime));
File.SetAttributes(_lockFile, FileAttributes.ReadOnly);
this.Show();
break;
}
catch (Exception)
{
_returnValue = false;
}
}
}
}
private void DeleteInstance()
{
try
{
File.SetAttributes(string.Concat(AppDomain.CurrentDomain.BaseDirectory, string.Format("/{0}", instanceFileName)), FileAttributes.Normal);
File.Delete(string.Concat(AppDomain.CurrentDomain.BaseDirectory, string.Format("/{0}", instanceFileName)));
}
catch (Exception)
{
}
}
private void Form_Shown(Object sender, EventArgs e)
{
_backWorker.RunWorkerAsync();
}
private void FormClosed(object sender, FormClosedEventArgs e)
{
DeleteInstance();
}
private void Form_Load(object sender, System.EventArgs e)
{
CheckInstance();
}
BackgroundWorker _backWorker = new BackgroundWorker();
public Form()
{
InitializeComponent();
_backWorker.WorkerReportsProgress = true;
_backWorker.ProgressChanged += _backWorker_ProgressChanged;
_backWorker.RunWorkerCompleted += _backWorker_RunWorkerCompleted;
_backWorker.DoWork += _backWorker_DoWork;
}
private void _backWorker_DoWork(object sender, DoWorkEventArgs e)
{
Do some work processing...
}
private void _backWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
this.Close();
}
private void _backWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
pg.Value = e.ProgressPercentage;
lblIndicator.Text = e.UserState.ToString();
}
When the exe run 3 instance, the first instance will run while 2nd and third hides for a while awaiting the 1st instance to be finisih. However, after the 1st instance finish the process, The 2nd and 3rd instance are running simultaneously.
Any Ideas? Thanks.
Maybe this can work:
public static bool IsProgramRunning(string TitleOfYourForm)
{
bool result = false;
Process[] processes = Process.GetProcesses();
foreach (Process p in processes)
{
if (p.MainWindowTitle.Contains(TitleOfYourForm))
{
result = true;
break;
}
}
return result;
}
Call this function in the Main function(before opening the mainForm), if it is false Application.Exit() else show your form..
If this answer helped you, vote me.
This case is using C# WPF. I want to instantly disable a button after clicking it to prevent clicking it twice in short succession. I disabled the button in OnClick_Event but still clickable.
Part of source is as below.
private void Button_Click_UpdateBurndownChart(object sender, RoutedEventArgs e)
{
if(threadNotWorking)
{
updateButton.IsEnabled = false;
startWorkThread();
}
}
private void startWorkThread()
{
... ...
//after finish required process
updateButton.IsEnabled = true;
}
Is there any way to accomplish this?
you may want to use a dispatcher, there is probably a threading problem (callback function running on seperate thread and trying to access ui which runs on another thread). try this . .
updateButton.Dispatcher.BeginInvoke(
new ThreadStart(() => updateButton.IsEnabled = false),
System.Windows.Threading.DispatcherPriority.Input, null);
instead of
updateButton.IsEnabled = false;
What happens if you were instead to change the order of your events from:
updateButton.IsEnabled = false;
startWorkThread();
To
startWorkThread();
updateButton.IsEnabled = false;
Let me know how this goes.
What it looks like is that you are starting your thread then immediatly enabling your button before your thread has finished. You would be better off using a BackgroundWorker and enable your Button in the RunWorkerCompleted Event. Though you can do something similar by enabling your button using a BeginInvoke at the end of your Process.
public void doWork()
{
System.Threading.Thread.Sleep(10000); //Simulating your Process
Dispatcher.BeginInvoke(new System.Threading.ThreadStart(delegate() { updateButton.IsEnabled = true; }), System.Windows.Threading.DispatcherPriority.Background);
}
Example with BackgroundWorker
using System.ComponentModel;
public partial class MainWindow : Window
{
BackgroundWorker bgw;
public MainWindow()
{
InitializeComponent();
bgw = new BackgroundWorker();
bgw.DoWork += new DoWorkEventHandler(bgw_DoWork);
bgw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bgw_RunWorkerCompleted);
}
void bgw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
updateButton.IsEnabled = true;
}
void bgw_DoWork(object sender, DoWorkEventArgs e)
{
System.Threading.Thread.Sleep(10000); //Simulating your work
}
private void startWorkThread()
{
bgw.RunWorkerAsync();
}
private void updateButton_Click(object sender, RoutedEventArgs e)
{
if (bgw.IsBusy != true)
{
updateButton.IsEnabled = false;
startWorkThread();
}
}
}