We've made an Application with a MainWindow called MV.
When main starts it launches our StartProgram method as a BackgroundWorker and the Application.Run(MW);
MainWindow MW = new MainWindow();
BackgroundWorker.DoWork += (obj, e) => StartProgram(MW);
BackgroundWorker.RunWorkerAsync();
Application.Run(MW);
In StartProgram we create instances of Patient, which we want to show in our listView1.
We do this by calling this method, which is in MW:
public void SetListSource(Patient p)
{
ListViewItem item = new ListViewItem("woohoo");
item.SubItems.Add("a");
listView1.Items.Add(item);
}
StartProgram stalls when it reaches listView1.Items.Add(item);
Our guess is, that it waits for MW (MainWindow), but we can't figure out how to fix it.
We have a button in MW, that does somethis similar, except it only sends "1" and "a" to the listView1.
private void Sort_Button_Click(object sender, EventArgs e)
{
ListViewItem item = new ListViewItem("1");
item.SubItems.Add("a");
listView1.Items.Add(item);
}
Does anybody know how to make SetListSource(...) work as Sort_Button_Click(...)?
EDIT
Solved with Invoke
You can't modify your GUI directly from another thread. You need to use a delegate and invoke your control. In your thread you have to do:
CONTROL.Invoke(new Action(() =>
{
CONTROL.Items.Add(item);
}
));
Source:
BackgroundWorker multithread access to form
You can use Invoke, but that's probably unnecessary. You can use BackgroundWorker.RunWorkerCompleted event instead:
BackgroundWorker.DoWork +=
(s, e) =>
{
e.Result = DoAllTheComplicatedWork();
}
BackgroundWorker.RunWorkerCompleted +=
(s, e) =>
{
// Back on the UI thread, we can do whatever we want
listView1.Items.Add(((SomeDTO)e.Result).Patient);
}
BackgroundWorker.RunWorkerAsync();
Or, you can do the whole thing using await:
MW.Load += async (s, e)
{
var result = await Task.Run(() => SomeCPUWork());
listView1.Items.Add(((SomeDTO)e.Result).Patient);
}
The key point is, you really want a separation between the UI and whatever you need to do in background. I definitely wouldn't pass a form (or any other control) to any method that's supposed to be executed on a different thread.
Related
I want to:
Show a form with a textbox.
Run an external program (notepad.exe for ease of example).
Continue to allow the user to enter data into the form textbox whilst notepad is running.
Run some more (continue) native form code when notepad closes. This will update the form, amongst other things.
I'm having problems making this happen. I'm aware of a multitude of posts about this similar issue, but haven't found a solution that works for me.
I have tried:
Doing a waitforexit, but this of course blocks the UI and users cannot enter data.
Attempting an asynchronous process call, where another method is called when this process is completed. This causes a problem where the new method is called from another thread and can't update the form.
Doing a wait/sleep loop in the UI, but again this will naturally block the UI.
What would be the neatest, and simplest solution for a simple Windows Form program? There are no extra classes used, and all code is in the Form1 class.
The Process class fires an Exited event when the process exits. You can add a handler to that event to execute code when the process exits without blocking the UI thread:
process.EnableRaisingEvents = true;
process.Exited += (s, args) => DoStuff();
Alternatively you could create a Task that represents the completion of the process to leverage the TPL for asynchrony:
public static Task WhenExited(this Process process)
{
var tcs = new TaskCompletionSource<bool>();
process.EnableRaisingEvents = true;
process.Exited += (s, args) => tcs.TrySetResult(true);
return tcs.Task;
}
This would allow you to write:
await process.WhenExited();
UpdateUI();
Here you go:
void Form1_Load(object sender, EventArgs e)
{
Task.Factory.StartNew(() =>
{
var p = Process.Start("notepad.exe");
p.WaitForExit();
}).ContinueWith(antecedant => { MessageBox.Show("Notepad closed"); });
}
Here is my favorite way to do something like this with a BackgroundWorker. This has the advantage of the RunWorkerCompleted callback being on the main thread, so it can interact with the UI.
public partial class Form1 : Form
{
...
private BackgroundWorker wrk;
private void button1_Click(object sender, EventArgs e)
{
wrk = new BackgroundWorker();
wrk.DoWork += (s, ea) => { /*Create your process and wait here*/ };
wrk.RunWorkerCompleted += (s, ea) => { textBox1.Text = "Finished"; };
wrk.RunWorkerAsync();
}
}
You should start process in BackgroundWorker so you can catch complete event on same thread.
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += delegate {
Process proc = Process.Start("YOUR-PROCESS-PATH");
proc.Start();
proc.WaitForExit();
}
worker.RunWorkerCompleted += worker_RunWorkerCompleted;
worker.RunWorkerAsync();
then catch the worker ended event on called thread;
void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
//Do your thing o UI thread
}
The following code makes UI thread hanging.
private void button1_Click(object sender, EventArgs e)
{
Thread t = new Thread(Func);
t.Start();
}
private void Func()
{
this.Invoke((Action)(() =>
{
while (true);
}));
}
I'd like to have Func() invoked in a different working thread without any UI thread freezing every time I click the button.
What would be the best workaround?
With your code, while(true) is running on UI thread, that is the reason which blocks your UI.
Put while(true) out of Invoke method, so whenver you want to change UI, put the block of code changing UI inside Invoke:
private void button1_Click(object sender, EventArgs e)
{
Thread t = new Thread(Func);
t.Start();
}
private void Func()
{
while(true)
{
this.Invoke((Action)(() =>
{
textBox.Text = "abc";
}));
}
}
The Func() codes does run on a non-UI thread. However, the this.Invoke then executes the Action on the UI thread!.
Try something like this:
void Func()
{
// Do some work.
// Update the UI (must be on UI thread)
this.Invoke(Action) (() =>
{
// Update the UI.
}));
}
I might be better to use the BeginInvoke method. This way the non-UI thread is not waiting around for the UI thread to do the Action.
Also, you have no Exception catching or progress reporting logic. I recommend looking at the BackgroundWorker class; http://msdn.microsoft.com/en-us/library/cc221403(v=vs.95).aspx.
void button1_Click(object sender, EventArgs e)
{
var worker = new BackgroundWorker();
worker.DoWork += (s,e) =>
{
// Do some work.
};
worker.RunWorkerCompleted += (s,e) =>
{
// Update the UI.
}
worker.RunWorkerAsync();
}
I have create a backgroundworker in an class it works, but if i call and wait until the end run, call it for the second time it will do the same process twice
i thinks there is somthing wrong with bw.DoWork +=
private void button1_Click(object sender, EventArgs e)
{
nptest.test.start("null", "null");
}
namespace nptest
{
class test
{
public static void start(string str, string strb)
{
if (bw.IsBusy != true)
{
bw.WorkerSupportsCancellation = true;
bw.DoWork += (obj, e) => bw_DoWork(str, strb);
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
bw.RunWorkerAsync();
}
}
private static BackgroundWorker bw = new BackgroundWorker();
private static void bw_DoWork(string str, string strb)
{
System.Windows.Forms.MessageBox.Show("initializing BackgroundWorker");
}
private static void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if ((e.Cancelled == true))
{
Console.WriteLine("Canceled");
}
else if (!(e.Error == null))
{
Console.WriteLine("Error: " + e.Error.Message);
}
bw.Dispose();
}
}
}
problem solved
class test
{
private static List<object> arguments = new List<object>();
// initializing with program startup
public static void bwinitializing()
{
bw.WorkerSupportsCancellation = true;
bw.DoWork += new DoWorkEventHandler(bw_DoWork);
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
}
public static void start(string str, string strb)
{
if (bw.IsBusy != true)
{
arguments.Clear();
arguments.Add(str);
arguments.Add(strb);
bw.RunWorkerAsync(arguments);
}
}
private static BackgroundWorker bw = new BackgroundWorker();
private static void bw_DoWork(object sender, DoWorkEventArgs e)
{
List<object> genericlist = e.Argument as List<object>;
System.Windows.Forms.MessageBox.Show("BackgroundWorker " + genericlist[0]);
}
I would suspect that multiple DoWork events are being inadvertently added.
That is, every time the start method is called it registers a new DoWork event handler. This adds and does not replace the existing handler DoWork handler. So then there will be multiple DoWork handlers called subsequent times .. 1, 2, 3, etc.
// creates a NEW delegate and adds a NEW handler
bw.DoWork += (obj, e) => bw_DoWork(str, strb);
I would recommend not using a closure here, but rather just use a Method Group (with implicit conversion to a delegate) and then pass the data to the RunWorkerAsync call (there is a form that takes an argument for data).
The RunWorkerCompleted += line doesn't have this issue because it is passed a delegate from a Method Group (which is guaranteed to always evaluate to the same delegate object1). Thus the repeated += calls for that line will replace the handler.
Example:
class MyData {
public string StrA { get; set; }
}
// These only need to be setup once (and should be for clarity).
// However it will be "ok" now if they are called multiple times
// as, since the delegates are the same, the += will
// act as a replacement (as it replaces the previous delegate with itself).
bw.WorkerSupportsCancellation = true;
bw.DoWork += bw_DoWork;
bw.RunWorkerCompleted += bw_RunWorkerCompleted;
// Pass data via argument
bw.RunWorkerAsync(new MyData {
StrA = str,
});
void bw_DoWork (object sender, DoWorkEventArgs e) {
var data = (MyData)e.Argument;
var str = data.StrA;
// stuff
}
1 I am not sure if it is guaranteed to be reference-equals equality, but using this approach allows for stable invoking of += and -= from the delegate from the Method Group even if obtained by new DelegateType(MethodGroup).
Wrt. my comment in the main post: if UI elements are accessed from a thread on which they were not created then there will fun "Cross-thread operation exceptions". I believe this usage of a Message Box is "okay" (when not created with an owner from another thread), but the practice of accessing the UI in a BackgroundWorker's DoWork is generally dubious.
Also, do not call bw.Dispose() here; dispose it with the owning container or context. It appears to be nice and benign in this case, but only do it when that BGW instance will never be used again. Calling it from an event handler is also dubious as the BGW is still "active".
I have encounter same problem as above commenter "Power-Mosfet"
and in the end, added a new BackgroundWorker() then assigned to the global bw value will fix my problem.
code is, change from:
private BackgroundWorker gBgwDownload;
private void yourFunction_bw(xxx)
{
// Create a background thread
gBgwDownload.DoWork += bgwDownload_DoWork;
gBgwDownload.RunWorkerCompleted += bgwDownload_RunWorkerCompleted;
//omited some code
gBgwDownload.RunWorkerAsync(paraObj);
}
to:
private BackgroundWorker gBgwDownload;
private void yourFunction_bw(xxx)
{
// Create a background thread
gBgwDownload = new BackgroundWorker(); /* added this line will fix problem */
gBgwDownload.DoWork += bgwDownload_DoWork;
gBgwDownload.RunWorkerCompleted += bgwDownload_RunWorkerCompleted;
//omited some code
gBgwDownload.RunWorkerAsync(paraObj);
}
There is also another reason. look for DoWorkEventHandler in its generated code InitializeComponent() If you have generated it through compnent UI properties and also registering it yourself.
Because if you register it again it will not override the previous one but will add another event and will call twice.
In my case, BackgroundWorker was running twice because in the constructor class of my form I declared the DoWork, ProgressChanged and RunWorkerCompleted event handlers, but it was already declared by Visual Studio 2013 in Designer part of this form class.
So, I just deleted my declarations and it worked fine.
thank you....this code is working fine... creating new intance for backroundworker is good idea....
Now we can call this function in for/while loop and can run multiple backgroundworker process.
I coded like this
when button click is done.. without distrubting the main thread flow... multiple process will be running back side....
i just used messagebox to pop up..but we can do timetaking process to run in "bgwDownload_DoWork" function... and multiple process will be created... and her we need not check the BackgroundWorker is busy or not...
private void button1_Click(object sender, EventArgs e)
{
for (int i = 0; i < 3; i++)
yourFunction_bw(i);
}
private BackgroundWorker gBgwDownload;
private void yourFunction_bw(int i)
{
// Create a background thread
gBgwDownload = new BackgroundWorker(); // added this line will fix problem
gBgwDownload.DoWork += bgwDownload_DoWork;
gBgwDownload.RunWorkerAsync(i);
}
private void bgwDownload_DoWork(object sender, DoWorkEventArgs e)
{
int stre = (int)e.Argument;
MessageBox.Show(stre.ToString ()); // time taken process can be added here
}
I ran into this problem today, I put a background worker on a popup form that was doing a long running task when I noticed that every time I showed the form the background worker RunWorkerCompleted event was being called multiple times.
My problem was that I was not disposing of the form after closing it, which meant every time I showed the form it added another handler to the even each time.
Disposing of the form when finished with it solved my problem. Just wanted to mention it here as I came across this page when I went looking for a solution for my situation.
I removed the control from the designer and instantiate a new WorkerProcess in Code:
example:
var bwProcess = new BackgroundWorker();
bwProcess.DoWork += new DoWorkEventHandler(bwProcess_DoWork);
bwProcess.RunWorkerCompleted += bwProcess_RunWorkerCompleted;
What should be straight forward is not here and I couldnt find a way yet in spite of reading a lot.
I have a button which executes a time consuming function. So on clicking the button should show time elapsed in milliseconds in a label with an interval of 500 ms. And when the desired result is achieved I want the timer to stop. I dont just need the final time (the total time consumed) in a label, but the label should dynamically show the time being elapsed. My code would be:
private void btnHistory_Click(object sender, EventArgs e)
{
Class1 c = new Class1();
c.StartClock(ref label12);
Utility.PopulateHistory(dgvRecords_history, _util); //time consuming function
c.StopClock();
}
And in Class1 I write this:
internal void StartClock(ref Label l)
{
Timer t = new Timer();
t.Interval = 500;
t.Enabled = true;
t.Tag = l;
t.Tick += new EventHandler(t_Tick);
t.Start();
}
int i;
bool stop;
void t_Tick(object sender, EventArgs e)
{
if (stop)
{
((Timer)sender).Stop();
return;
}
((Label)((Timer)sender).Tag).Text = (++i).ToString();
}
internal void StopClock()
{
i = 0;
stop = true;
}
What happens is, the t_Tick event is fired only after the complete code under button event is fired. That is the tick event is fired after it goes through the StopClock function! I got no idea why on earth it should be that!
2 questions basically:
How can my requirement be achieved in the right way to handle these? I know I should use other built in classes to evaluate performance, but this is just for display purpose. For this, what is the ideal approach?
Why is my code not working?
EDIT: I have used here System.Windows.Forms Timer here, but the result is not any different with System.Timers Timer
The problem is that your long-running task is also running on the UI thread. So the timer can't fire and update the UI, since the thread is busy handling the long-running task.
Instead, you should use a BackgroundWorker to handle the long-running task.
In code:
private void btnHistory_Click(object sender, EventArgs e)
{
Class1 c = new Class1(ref label12);
c.StartClock();
var backgroundWorker = new BackgroundWorker();
backgroundWorker.DoWork += (s, e) =>
{
// time consuming function
Utility.PopulateHistory(dgvRecords_history, _util);
};
backgroundWorker.RunWorkerCompleted += (s, e) =>
{
c.StopClock();
};
backgroundWorker.RunWorkerAsync();
}
As ChrisWue noted, since you now have the long-running task in a separate thread, it needs to invoke any access to the UI controls on the UI thread.
If your long-running task just needs some data from the UI to start, you can pass that data as parameter of RunWorkerAsync(). If you need to output some result data to the UI, you can do that in the handler of the RunWorkerCompleted event. If you occasionally need to update the UI as progress is being made, you can do that in the handler of the ProgressChanged event, calling ReportProgress() in your DoWork handler.
If none of the above are needed, you could use the ThreadPool, as in StaWho's answer.
Your time consuming function is blocking the main thread. You can use BackgroundWorker or below trick:
public Form1()
{
InitializeComponent();
t.Tick +=new EventHandler(t_Tick);
t.Interval = 500;
}
int timeElapsed = 0;
System.Windows.Forms.Timer t = new System.Windows.Forms.Timer();
private void button1_Click(object sender, EventArgs e)
{
t.Start();
ThreadPool.QueueUserWorkItem((x) =>
{
TimeConsumingFunction();
});
}
void TimeConsumingFunction()
{
Thread.Sleep(10000);
t.Stop();
}
void t_Tick(object sender, EventArgs e)
{
timeElapsed += t.Interval;
label1.Text = timeElapsed.ToString();
}
Add the timer to the Components collection of the form. Or store the timer in a field in the class.
The timer is garbage collected because it is not longer reachable when your method returns.
I don't know about your long running code, but out should new run on a separate thread, or make calls to Application.DoEvents
(And remove the ref in your code, it is not used).
#Dainel Rose's answer worked for me perfectly, but only if invalid cross thread operation is handled. I could do so like:
private void btnHistory_Click(object sender, EventArgs e)
{
Class1 c = new Class1(ref label12);
c.StartClock();
var backgroundWorker = new BackgroundWorker();
backgroundWorker.DoWork += ((s, e) =>
{
// time consuming function
Utility.PopulateHistory(dgvRecords_history, _util);
});
backgroundWorker.RunWorkerCompleted += ((s, e) =>
{
c.StopClock();
});
backgroundWorker.RunWorkerAsync();
}
And in the Utility class where the time consuming function runs,
internal static void PopulateHistory(DataGridView dgv, Utility util)
{
SetDataGridView_History(dgv, util);
}
delegate void UpdateDataGridView_History(DataGridView dgv, Utility util);
static void SetDataGridView_History(DataGridView dgv, Utility util)
{
if (dgv.InvokeRequired)
{
UpdateDataGridView_History updaterDelegate = new UpdateDataGridView_History(SetDataGridView_History);
((Form)util._w).Invoke(updaterDelegate, new object[] { dgv, util });
}
else
//code that utilizes UI thread (long running process in my case)
}
Thanks all who helped. I'm marking Daniel's answer..
I have spent the whole day trying to make my application use threads but with no luck. I have read much documentation about it and I still get lots of errors, so I hope you can help me.
I have one big time consuming method which calls the database and updates the GUI. This has to happen all the time(or about every 30 seconds).
public class UpdateController
{
private UserController _userController;
public UpdateController(LoginController loginController, UserController userController)
{
_userController = userController;
loginController.LoginEvent += Update;
}
public void Update()
{
BackgroundWorker backgroundWorker = new BackgroundWorker();
while(true)
{
backgroundWorker.DoWork += new DoWorkEventHandler(backgroundWorker_DoWork);
backgroundWorker.RunWorkerAsync();
}
}
public void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
_userController.UpdateUsersOnMap();
}
}
With this approach I get an exception because the backgroundworker is not and STA thread(but from what I can understand this is what I should use). I have tried with a STA thread and that gave other errors.
I think the problem is because I try to update the GUI while doing the database call(in the background thread). I should only be doing the database call and then somehow it should switch back to the main thread. After the main thread has executed it should go back to the background thread and so on. But I can't see how to do that.
The application should update the GUI right after the database call. Firering events don't seem to work. The backgroundthread just enters them.
EDIT:
Some really great answers :) This is the new code:
public class UpdateController{
private UserController _userController;
private BackgroundWorker _backgroundWorker;
public UpdateController(LoginController loginController, UserController userController)
{
_userController = userController;
loginController.LoginEvent += Update;
_backgroundWorker = new BackgroundWorker();
_backgroundWorker.DoWork += backgroundWorker_DoWork;
_backgroundWorker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted;
}
public void _backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
_userController.UpdateUsersOnMap();
}
public void Update()
{
_backgroundWorker.RunWorkerAsync();
}
void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
//UI update
System.Threading.Thread.Sleep(10000);
Update();
}
public void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
// Big database task
}
}
But how can I make this run every 10 second? System.Threading.Thread.Sleep(10000) will just make my GUI freeze and while(true) loop in Update() as suggested gives an exception(Thread too busy).
You need to declare and configure the BackgroundWorker once - then Invoke the RunWorkerAsync method within your loop...
public class UpdateController
{
private UserController _userController;
private BackgroundWorker _backgroundWorker;
public UpdateController(LoginController loginController, UserController userController)
{
_userController = userController;
loginController.LoginEvent += Update;
_backgroundWorker = new BackgroundWorker();
_backgroundWorker.DoWork += new DoWorkEventHandler(backgroundWorker_DoWork);
_backgroundWorker.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker_ProgressChanged);
_backgroundWorker.WorkerReportsProgress= true;
}
public void Update()
{
_backgroundWorker.RunWorkerAsync();
}
public void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
while (true)
{
// Do the long-duration work here, and optionally
// send the update back to the UI thread...
int p = 0;// set your progress if appropriate
object param = "something"; // use this to pass any additional parameter back to the UI
_backgroundWorker.ReportProgress(p, param);
}
}
// This event handler updates the UI
private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
// Update the UI here
// _userController.UpdateUsersOnMap();
}
}
You have to use the Control.InvokeRequired property to determine if you are on a background thread. Then you need to invoke your logic that modified your UI via the Control.Invoke method to force your UI operations to occur on the main thread. You do this by creating a delegate and passing it to the Control.Invoke method. The catch here is you need some object derived from Control to call these methods.
Edit: As another user posted, if yo you can wait to the BackgroundWorker.Completed event to update your UI then you can subscribe to that event and call your UI code directly. BackgroundWorker_Completed is called on the main app thread. my code assumes you want to do updates during the operation. One alternative to my method is to subscribe to the BwackgroundWorker.ProgressChanged event, but I believe you'll need to still call Invoke to update your UI in that case.
for example
public class UpdateController
{
private UserController _userController;
BackgroundWorker backgroundWorker = new BackgroundWorker();
public UpdateController(LoginController loginController, UserController userController)
{
_userController = userController;
loginController.LoginEvent += Update;
}
public void Update()
{
// The while loop was unecessary here
backgroundWorker.DoWork += new DoWorkEventHandler(backgroundWorker_DoWork);
backgroundWorker.RunWorkerAsync();
}
public delegate void DoUIWorkHandler();
public void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
// You must check here if your are executing on a background thread.
// UI operations are only allowed on the main application thread
if (someControlOnMyForm.InvokeRequired)
{
// This is how you force your logic to be called on the main
// application thread
someControlOnMyForm.Invoke(new
DoUIWorkHandler(_userController.UpdateUsersOnMap);
}
else
{
_userController.UpdateUsersOnMap()
}
}
}
You should remove the while(true), you are adding infinite event handlers and invoking them infinite times.
You can use the RunWorkerCompleted event on the backgroundWorker class to define what should be done when the background task has completed. So you should do the database call in the DoWork handler, and then update the interface in the RunWorkerCompleted handler, something like this:
BackgroundWorker bgw = new BackgroundWorker();
bgw.DoWork += (o, e) => { longRunningTask(); }
bgw.RunWorkerCompleted += (o, e) => {
if(e.Error == null && !e.Cancelled)
{
_userController.UpdateUsersOnMap();
}
}
bgw.RunWorkerAsync();
In addition to previous comments, take a look at www.albahari.com/threading - best doc on threading you will ever find. It will teach you how to use the BackgroundWorker properly.
You should update the GUI when the BackgroundWorker fires Completed event (which is invoked on UI thread to make it easy for you, so that you don't have to do Control.Invoke yourself).
Here's a source code pattern you can use based on some WinForms example code, but you can apply it for WPF as well very easily. In this example, I am redirecting output to a Console which I then use to let the background worker write some messages to a textbox while it is processing.
It consists of:
A helper class TextBoxStreamWriter used to redirect console output to a textbox
A background worker writing to the redirected console
A progress bar which needs to be reset after completion of background worker
Some text boxes (txtPath and txtResult), and a "Start" button
In other words, there is some background task which needs to interact with the UI. Now I am going to show how that is done.
From the context of the background task, you need to use Invoke to access any UI element. I believe the simplest way to do that is to use lambda expression syntax, like
progressBar1.Invoke((Action) (() =>
{ // inside this context, you can safely access the control
progressBar1.Style = ProgressBarStyle.Continuous;
}));
To update the ProgressBar, a local method like
private void UpdateProgress(int value)
{
progressBar1.Invoke((Action)(() => { progressBar1.Value = value; }));
}
helps. It is passing the value parameter to the progress bar as a closure.
This is the helper class TextBoxStreamWriter, which is used to redirect console output:
public class TextBoxStreamWriter : TextWriter
{
TextBox _output = null;
public TextBoxStreamWriter(TextBox output)
{
_output = output;
}
public override void WriteLine(string value)
{
// When character data is written, append it to the text box.
// using Invoke so it works in a different thread as well
_output.Invoke((Action)(() => _output.AppendText(value+"\r\n")));
}
}
You need to use it in the form load event as follows (where txtResult is a textbox, to which the output will be redirected):
private void Form1_Load(object sender, EventArgs e)
{
// Instantiate the writer and redirect the console out
var _writer = new TextBoxStreamWriter(txtResult);
Console.SetOut(_writer);
}
There is also a button on the form which starts the background worker, it passes a path to it:
private void btnStart_Click(object sender, EventArgs e)
{
backgroundWorker1.RunWorkerAsync(txtPath.Text);
}
This is the workload of the background worker, note how it uses the console to output messages to the textbox (because of the redirection that was set up earlier):
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
var selectedPath = e.Argument as string;
Console.Out.WriteLine("Processing Path:"+selectedPath);
// ...
}
The variable selectedPath consists of the path that was passed to the backgroundWorker1 earlier via the parameter txtPath.Text, it is being accessed via e.Argument.
If you need to reset some controls afterwards, do it in the following way (as already mentioned above):
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
progressBar1.Invoke((Action) (() =>
{
progressBar1.MarqueeAnimationSpeed = 0;
progressBar1.Style = ProgressBarStyle.Continuous;
}));
}
In this example, after completion, a progress bar is being reset.
Important: Whenever you access a GUI control, use Invoke as I did in the examples above.
Using Lambda's makes it easy, as you could see in the code.
And here's the complete example, which runs in LinqPad 6 (just copy and paste it into an empty C# Program query) - I decided to use LinqPad this time so you can learn something new, because you all know how to create a new Windows Forms project in Visual Studio (and if you still want to do so, just copy the events below and drag and drop the controls to the form):
// see: https://stackoverflow.com/a/27566468/1016343
using System.ComponentModel;
using System.Windows.Forms;
BackgroundWorker backgroundWorker1 = new System.ComponentModel.BackgroundWorker();
ProgressBar progressBar1 = new ProgressBar() { Text = "Progress", Width = 250, Height=20, Top=10, Left=0 };
TextBox txtPath = new TextBox() { Text =#"C:\temp\", Width = 100, Height=20, Top=30, Left=0 };
TextBox txtResult = new TextBox() { Text = "", Width = 200, Height=250, Top=70, Left=0, Multiline=true, Enabled=false };
Button btnStart = new Button() { Text = "Start", Width = 100, Height=30, Top=320, Left=0 };
void Main()
{
// see: https://www.linqpad.net/CustomVisualizers.aspx
// Instantiate the writer and redirect the console out
var _writer = new TextBoxStreamWriter(txtResult);
Console.SetOut(_writer);
// wire up events
btnStart.Click += (object sender, EventArgs e) => btnStart_Click(sender, e);
backgroundWorker1.DoWork += (object sender, DoWorkEventArgs e) => backgroundWorker1_DoWork(sender, e);
backgroundWorker1.RunWorkerCompleted += (object sender, RunWorkerCompletedEventArgs e)
=> backgroundWorker1_RunWorkerCompleted(sender, e);
using var frm = new Form() {Text="Form", Width = 300, Height=400, Top=0, Left=0};
frm.Controls.Add(progressBar1);
frm.Controls.Add(txtPath);
frm.Controls.Add(txtResult);
frm.Controls.Add(btnStart);
// display controls
frm.ShowDialog();
}
private void btnStart_Click(object sender, EventArgs e)
{
backgroundWorker1.RunWorkerAsync(txtPath.Text);
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
InitProgress();
var selectedPath = e.Argument as string;
Console.Out.WriteLine("Processing Path: " + selectedPath);
UpdateProgress(0); Thread.Sleep(300); UpdateProgress(30); Thread.Sleep(300);
UpdateProgress(50); Thread.Sleep(300);
Console.Out.WriteLine("Done.");
// ...
}
private void UpdateProgress(int value)
{
progressBar1.Invoke((Action)(() =>
{
progressBar1.Value = value;
}));
}
private void InitProgress()
{
progressBar1.Invoke((Action)(() =>
{
progressBar1.MarqueeAnimationSpeed = 0;
progressBar1.Style = ProgressBarStyle.Continuous;
}));
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
UpdateProgress(100); // always show 100% when done
}
// You can define other methods, fields, classes and namespaces here
public class TextBoxStreamWriter : TextWriter
{
TextBox _output = null;
public TextBoxStreamWriter(TextBox output)
{
_output = output;
}
public override Encoding Encoding => throw new NotImplementedException();
public override void WriteLine(string value)
{
// When character data is written, append it to the text box.
// using Invoke so it works in a different thread as well
_output.Invoke((Action)(() => _output.AppendText(value + "\r\n")));
}
}
The if-statement in #Lee's answer should look like:
bgw.RunWorkerCompleted += (o, e) => {
if(e.Error == null && !e.Cancelled)
{
_userController.UpdateUsersOnMap();
}
}
...if you want to invoke UpdateUsersOnMap(); when there are no errors and BgWorker hasn't been cancelled.