Develop Reference

Threading in my windows form app is still freezing my UI

Background
Currently working on a windows form app which I asked to create. I have ran into an issue where the UI freezes when a resource intensive process is being called. I am currently using threading from which I understand is used to prevent the UI from freezing and taking over the entire pc.
Question
Currently when I am using threading to call a method in my base class which is to open a file that is located on a remote server. This method has a delay of approximately 30 to 45 seconds. I am creating my background thread and invoking it to start. When invoked to start if fires, however when it fired it would not wait for my thread to complete basically giving me a null exception. So after some digging I found that in order to wait for the thread to complete you had to invoke the .Join(). However when the Join is invoked it froze my UI completely. So my ingenuity tried to create a work around and created a while loop that would until the thread is no longer alive and continue. However, this also froze the UI. So am I missing something? That is not mention in MSDN Doc
Code Sample
class BaseClass
{
public CWClient ClientFileContext(string clientFile, bool compress)
{
Client clientContext = null;
try
{
if (compress == true)
{
clientContext = appInstance.Clients.Open2(clientFile, superUser, passWord, OpenFlags.ofCompressed);
}
else
{
clientContext = appInstance.Clients.Open2(clientFile, superUser, passWord, OpenFlags.ofNone);
}
}
catch (Exception ex)
{
//TODO
}
return clientContext;
}
}
public partial class Form1 : Form
{
private void button1_Click(object sender, EventArgs e)
{
BaseClass wpSec = new BaseClass();
CWClient client = null;
Thread backgroundThread = new Thread(
new ThreadStart(() =>
{
client = wpSec.ClientFileContext(selectedFileFullPath, true);
}
));
backgroundThread.Start();
//backgroundThread.Join(); << Freezes the UI
var whyAreYouNotWorking = "Stop";
}
}
Work around I tried
while (backgroundThread.IsAlive == true)
{
for (int n = 0; n < 100; n++)
{
Thread.Sleep(500);
progressBar1.BeginInvoke(new Action(() => progressBar1.Value = n));
}
}
// This also freezes the UI

I would also look into the async and await pattern for this. Explained in this post: Using async await still freezes GUI
Your code should be similar to this (Baseclass doesn't change) :
public partial class Form1 : Form
{
private async void button1_Click(object sender, EventArgs e)
{
BaseClass wpSec = new BaseClass();
CWClient client = await Task.Run(() =>
{
return wpSec.ClientFileContext(selectedFileFullPath, true);
}
);
var whyAreYouNotWorking = "Stop";
}
}
This is back-of-the-envelope stuff, but hopefully that gives the basic idea of launching a task, then awaiting the result in an async method. If you don't need your BaseClass hanging around, that can be in the lambda too, leaving you only what you really want.
That link from #Chris Dunaway above is also excellent. http://blog.stephencleary.com/2013/08/taskrun-vs-backgroundworker-round-3.html
Edit: As #BradlyUffner mentions, this is also one of the few times you should use async void and should rather prefer returning Task or Task<T> in virtually all other circumstances.

Unable to modify variables from separate thread

So I'm making a C# app which has to continuously read and display the contents of a text file, while allowing the user to enter something into a text box and append it to the end of that very file.
I'm doing this by running my read method on a separate thread, however changing the variable which stores the display text-files contents is what's causing a problem. Initially I tried having a method which did this, however that's not working and gave a 'cross-thread-operation-not-valid' error. I then tried applying some code I found on MSDN, but now after updating the variable once the thread ended!
Please help.
partial class MainForm
{
delegate void SetTextCallback(string text);
public static string msg;
public static string name;
public void InitClient()
{
name = "public.txt";
Console.WriteLine(name);
if(!File.Exists(name))
{
File.Create(name);
File.AppendAllText(name, "Welcome to " + name);
}
Thread Read = new Thread(new ThreadStart(this.Client));
Read.Start();
while(!Read.IsAlive);
}
public void WriteText()
{
File.AppendAllText(name, this.InputBox.Text);
this.InputBox.Clear();
}
private void SetText(string text)
{
if (this.OutPut.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else
{
this.OutPut.Text = text;
}
}
public void Client()
{
msg = File.ReadAllText(name);
Console.WriteLine(msg);
Thread.Sleep(300);
this.SetText(msg);
}
}
Why is the thread behaving like this. How can I modify my code so that the contents of the output box always equals that of the text file.
Any suggestions welcome.

You've got multiple problems here,
the use of the File is probably not thread-safe.
your method does not repeat
your are Sleep()ing on a Thread
You can solve all of them by ditching the Thread and use a simple Timer.

Try using a background worker instead of creating a new thread. The background worker will run its content in a seperate thread, and allows you to report 'progress' while its working. This progress report will always be run on the UI-thread (or the thread which started the background worker).
It also has an event which is called when the background worker is finished. This is also run on the UI thread.
This example should get you started.
Update: Added some very basic error handling as suggested
The idea is to use the UserData (2nd argument) of ReportProgress to do updates on the UI thread whenever you need to. In this case it is a string, but this can be any object.
Furthermore, you can use the Result of the DoWorkEventArgs to produce a final result from the background work. In this case, I return any exception which was thrown, or null otherwise, but you can return whatever you want here as well.
It is, as Henk mentioned in his comment, very important to handle errors that occur inside the DoWork callback, because exceptions etc which occurs here will be swallowed and the worker will complete as if nothing bad happened.
private BackgroundWorker _backgroundWorker;
public Form1()
{
InitializeComponent();
_backgroundWorker = new BackgroundWorker();
_backgroundWorker.WorkerReportsProgress = true;
_backgroundWorker.WorkerSupportsCancellation = true;
// This is the background thread
_backgroundWorker.DoWork += BackgroundWorkerOnDoWork;
// Called when you report progress
_backgroundWorker.ProgressChanged += BackgroundWorkerOnProgressChanged;
// Called when the worker is done
_backgroundWorker.RunWorkerCompleted += BackgroundWorkerOnRunWorkerCompleted;
}
private void BackgroundWorkerOnRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs runWorkerCompletedEventArgs)
{
if (runWorkerCompletedEventArgs.Result != null)
{
// Handle error or throw it
throw runWorkerCompletedEventArgs.Result as Exception;
}
textBox1.Text = "Worker completed";
}
private void BackgroundWorkerOnProgressChanged(object sender, ProgressChangedEventArgs progressChangedEventArgs)
{
textBox1.Text = progressChangedEventArgs.UserState as string;
}
private void BackgroundWorkerOnDoWork(object sender, DoWorkEventArgs doWorkEventArgs)
{
try
{
for (int i = 0; i < 100 && !_backgroundWorker.CancellationPending; i++)
{
_backgroundWorker.ReportProgress(0, i + " cycles");
Thread.Sleep(100);
}
}
catch (Exception ex)
{
doWorkEventArgs.Result = ex;
}
}
private void startButton_Click(object sender, EventArgs e)
{
if (!_backgroundWorker.IsBusy)
_backgroundWorker.RunWorkerAsync();
}
private void cancelButton_Click(object sender, EventArgs e)
{
if(_backgroundWorker.IsBusy)
_backgroundWorker.CancelAsync();
}

how to include mutliple threading in this script

I am working on a project which includes two main processing, I have tried using timer_tick to handle the processing which makes the application really slow. The application needs to be running at all times, I wanted the timer aspect of the timer_tick to trigger the methods every X seconds but with the multiple threading, as this makes it a lot faster.
Can anyone help?
The current structure of the application is below:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
setting_info();
}
public void setting_info()
{
// takes data from config file for API connections
}
private void swis()
{
// connects to API and fetches data
// need to be continuously running - Ideally Interval(1200)
}
private void st_processing()
{
// processes the data that was fetched in swis() slows down the program without multiple threading
// need to be continuously running - Ideally Interval(800)
}
private void alert_in_timer_Tick(object sender, EventArgs e)
{
while (alert_in == true)
{
swis();
break;
}
}
private void st_processing_timer_Tick(object sender, EventArgs e)
{
while (st_processing == true && alert_data_database_has_data == true)
{
st_processing();
//check_error_count();
alert_data_database_has_data = false;
break;
}
}
}

It's not clear what you want to know. There are many good threading tutorials for C# as discussed here for example this one
Starting a thread is easy
Thread worker = new Thread(new ThreadStart(swis));
//...
worker.join();
You will need to be careful if you need to update the GUI as a result of what the thread does. Previously discussed here.
At the moment you break from the alert_in_timer_Tick once it's called the swis function.
while (alert_in == true)
{
swis();
break;// why is this here?
}

Button Text, Inconsistent

Why does my first attempt to change a button's text in this code not work, while the third attempt does work ?
My user will have to wait a few seconds while the serial port connects. After that, I want to alert him that he has already connected (a second attempt can cause problems).
I wanted to let him know that things are okay, so he won't think "duh" and click twice.
Fail. The text change never appears.
Okay, why does the third change in button text work, but the first one does not ? I don't know if the second one works or not.
/***********************************************************************
* Button: Connect Port *
***********************************************************************/
private void TheConnectPortButton_Click(object sender, EventArgs e)
{
string OldText = TheConnectPortButton.Text;
TheConnectPortButton.Text = "Busy, Please Wait"; /////// This never happens
ButtonBoss.ButtonHandler_ConnectPort();
TheConnectPortButton.Text = OldText; /////// Not sure if this happens
if (aUartSemaphoreThatTells.IfWeHaveConnectedToAPort == (int)aValueWhichIndicatesThat.YesWeHaveAGoodPortConnected)
{
TheConnectPortButton.Text = "Connected"; /////// This one does happen
}
}
the aUartSemaphoreThatTells.IfWeHaveConnectedToAPort is also used by the ButtonBoss routine to make sure he doesn't connect a second time, along with other button routines (e.g., make sure we are connected before we Tx/Rx or whatever).
I tried changing the code after the routine returns to look like this...
if (aUartSemaphoreThatTells.IfWeHaveConnectedToAPort == (int)aValueWhichIndicatesThat.YesWeHaveAGoodPortConnected)
{
TheConnectPortButton.Text = "Connected";
}
else
{
TheConnectPortButton.Text = OldText;
}
...and I still get the same result.
My guess (and that's all it is) is that threading is somehow involved in all this, and that the serial port routines trump the button text changing routines by some convolution that I don't follow properly at the moment.
Question: What do I need to do to get the text to change before the connection stuff hogs the system ?
(If that's what's happening)
Question 2: If I can't make this happen, I think I've read about "greying out" the buttons, or, I believe I saw somewhere that I can actually make a button go away right before the user's eyes so that he can't click it again. Links to example code would be welcome.

The problem is you're doing everything from one and the same event-handler consequently, so that the button has no time to get updated (redrawn). You could call Application.DoEvents(); method, but it's not a good idea at all, please, read Use of Application.DoEvents()
I think usually you're expected to push a time-consuming task into a separate thread, get progress report from it and update your GUI. There is a plenty of ways to create a "worker" thread and get some respond from it. For example, use a BackgroundWorker Class:
public partial class Form1 : Form
{
public Form1() { InitializeComponent(); }
private void button1_Click(object sender, EventArgs e)
{
BackgroundWorker w = new BackgroundWorker();
w.WorkerReportsProgress = true;
w.DoWork += new DoWorkEventHandler(w_DoWork);
w.ProgressChanged += new ProgressChangedEventHandler(w_ProgressChanged);
w.RunWorkerCompleted += new RunWorkerCompletedEventHandler(w_RunWorkerCompleted);
w.RunWorkerAsync();
button1.Text = "Started";
}
//may influence GUI, as this event handler is run on the GUI thread
void w_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
button1.Text = "Job is done";
}
//may influence GUI, as this event handler is run on the GUI thread
void w_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
button1.Text = e.ProgressPercentage.ToString();
}
//runs in the worker thread...should do the actual job
//may influence GUI through `ReportProgress`
//or through `Invoke` method
void w_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
for (int i = 1; i <= 10; i++)
{
Thread.Sleep(500);
worker.ReportProgress(10 * i);
}
}
}
Or you may use Task Class:
public partial class Form1 : Form
{
public Form1() { InitializeComponent(); }
private void button1_Click(object sender, EventArgs e)
{
new Task(DoTask).Start();
}
void DoTask()
{
for (int i = 1; i <= 10; i++)
{
Thread.Sleep(500);
//here you need to update GUI through `Invoke` method
//as the GUI may only be influenced from the the thread,
//where it's created
this.Invoke(new Action<int>((j) =>
{
button1.Text = j.ToString();
}), 10 * i);
}
}
}

Progress Dialog hangs in Outlook add-in using DoEvents

Background:
I am using a simple progress dialog in an Outlook Add-in to show progress while performing long operations. Since I cannot run code that uses Outlook objects in a separate thread, I cannot implement a more traditional background worker process. My add-in has been working OK until Outlook 2013 where in certain instances my progress dialog hangs. When I run the add-in in the VS debugger and cause the hang, then do a break, it appears to be stuck on the DoEvents() line that tries to force the progressbar to update.
My Question:
Can someone suggest a better system to show progress with the restriction above (long running code must run in main Outlook thread). Is there a better way to make the progress dialog responsive without using DoEvents()?
The following simple code demonstrates how I am doing this now. In the add-in code that is performing long operations on Outlook objects:
private void longRunningProcess()
{
int max = 100;
DlgStatus dlgstatus = new DlgStatus();
dlgstatus.ProgressMax = max;
dlgstatus.Show();
for (int i = 0; i < max; i++)
{
//Execute long running code that MUST best run in the main (Outlook's) thread of execution...
System.Threading.Thread.Sleep(1000); //for simulation purposes
if (dlgstatus.Cancelled) break;
dlgstatus.SetProgress("Processing item: " + i.ToString(), i);
}
}
Here's the code for the simple progress dialog window:
public partial class DlgStatus : Form
{
private bool _cancelled;
public DlgStatus()
{
InitializeComponent();
}
public int ProgressMax
{
set
{
progress.Maximum = value;
Application.DoEvents();
}
}
public bool Cancelled
{
get { return _cancelled; }
}
public void SetProgress(string status, int val)
{
lblStatus.Text = status;
progress.Value = val;
Application.DoEvents(); //Seems to hang here
}
private void btnCancel_Click(object sender, EventArgs e)
{
_cancelled = true;
Application.DoEvents();
this.Visible = false;
}
}

I was able to accomplish this by doing the following. The Custom form has a progressbar with the style set to Marquee.
I got the general method from http://social.msdn.microsoft.com/Forums/en/vsto/thread/59993421-cbb5-4b7b-b6ff-8a28f74a1fe5 but found that I did not need to use all the custom window handles.
private void btn_syncContacts_Click(object sender, RibbonControlEventArgs e)
{
Thread t = new Thread(SplashScreenProc);
t.Start();
//long running code
this.SyncContacts();
syncingSplash.Invoke(new Action(this.syncingSplash.Close), null);
}
private SyncingContactsForm syncingSplash = new SyncingContactsForm();
internal void SplashScreenProc(object param)
{
this.syncingSplash.ShowDialog();
}
It is important to note that the form does not work with the Outlook object model. It is not recommended by Microsoft to use the object model on separate threads.