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How to use a BackgroundWorker?
(2 answers)
Closed 1 year ago.
Hello I have a function which takes time to load. that's why i'm planning to put a progress bar on my winform so that the user would know that my program is still running. however, I do not know how I'm gonna solve it. is there someone here who could help guide me.
Here's what I'm planning to do:
private void btnProcess_Click(object sender, EventArgs e)
{
//function which takes time because it contacts to a server
}
I want to have a progressbar which increments and ends after my process has finished. Should I use a backgroundworker for this?
***I've followed this tutorial http://www.codeproject.com/Tips/83317/BackgroundWorker-and-ProgressBar-demo but it does not wait for a specific function or event to finish like a loading screen.
***My progressbar does not end after my buttonclick event has finished executing all its functions.
I've created:
private void myBackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i <= 100; i++)
{
myBackgroundWorker.ReportProgress(i);
System.Threading.Thread.Sleep(100);
}
}
private void myBackgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
myProgressBar.Value = e.ProgressPercentage;
}
private void btnProcess_Click(object sender, EventArgs e)
{
myBackgroundWorker.RunWorkerAsync();
//function which takes time because it contacts to a server
}
How Would I know when will my buttonclick event gonna end? so that my progress bar will end also?
These are the two really good examples
http://www.dreamincode.net/forums/topic/112547-using-the-backgroundworker-in-c%23/
http://www.dreamincode.net/forums/topic/246911-c%23-multi-threading-in-a-gui-environment/
Hope that helps
EDIT:
public partial class Form1 : Form
{
//--------------------------------------------------------------------------
public Form1()
{
InitializeComponent();
//Initialize backgroundworker
Shown += new EventHandler(Form1_Shown);
backgroundWorker1.WorkerReportsProgress = true;
backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
backgroundWorker1.ProgressChanged +=
new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
//counter
YourObject.Counter = 100;
}
//--------------------------------------------------------------------------
void btnClick_Clicked(object sender, EventArgs e)
{
//Trigger the background process
backgroundWorker1.RunWorkerAsync();
}
//--------------------------------------------------------------------------
void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
//Your freakishly long process,
//which needs to be run in the background
//to make it simple, I'll just do a for loop
for (int i = 0; i < 100; i++)
{
//The counter will keep track of your process
//In your case, it might not be a for loop
//So you will have to decide how to keep track of this counter
//My suggestion is to decrease/increase this counter
//right after importants action of your process
backgroundWorker1.ReportProgress(YourObject.Counter--);
}
}
void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
//The counter is updated and displayed with a progress bar
YourObject.Counter = e.ProgressPercentage;
}
}
Yeah, you should. It's pretty straightforward.
Make a background worker that executes whatever work btnProcess_Click does.
Have it report progress:
worker.WorkerReportsProgress = true;
And now you can have this progress report be triggered by an event you subscribe to.
worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);
In doing so, you can create a progress bar than can update itself based on this worker_ProgressChanged event, triggered by your computation.
You can find plenty of implementations of this just by Googling. Good luck, hope this helps.
Related
First page
private void Button_Click(object sender, RoutedEventArgs e)
{
Page1 p1 = new Page1();
this.NavigationService.Navigate(p1);
}
Second Page(Page 1 as specified in the code )
public Page1()
{
InitializeComponent();
Thread.Sleep(10000);
}
get loading icon or progress bar while navigating from page 3 to page 1 on button click.
As soon as the user clicks on the button on page 3 this page hangs until page 1 processes the data in the background
Code will be preferable
i have found this example at codeproject you give a look to the example. I hope this is help
How to set progress bar during one page to another page load in c# .net windows application?
This gets asked almost daily so I've written this short demonstration code to demonstrate how to use a System.ComponentModel.BackgroundWorker in combination with a System.Windows.Forms.ProgressBar. All the code is commented so the flow/steps should be easy to understand.
Just drop a ProgressBar (progressBar1) and a BackgroundWorker (backgroundWorker1) onto your form and copy and paste this code to see it in action.
Hide Shrink Copy Code
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
Shown += new EventHandler(Form1_Shown);
// To report progress from the background worker we need to set this
property
backgroundWorker1.WorkerReportsProgress = true;
// This event will be raised on the worker thread when the worker starts
backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
// This event will be raised when we call ReportProgress
backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
}
void Form1_Shown(object sender, EventArgs e)
{
// Start the background worker
backgroundWorker1.RunWorkerAsync();
}
// On worker thread so do our thing!
void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
// Your background task goes here
for (int i = 0; i <= 100; i++)
{
// Report progress to 'UI' thread
backgroundWorker1.ReportProgress(i);
// Simulate long task
System.Threading.Thread.Sleep(100);
}
}
// Back on the 'UI' thread so we can update the progress bar
void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
// The progress percentage is a property of e
progressBar1.Value = e.ProgressPercentage;
}
}
I'm working on a utility to copy a directory to multiple USB sticks. When Form1 loads, I would like for a label to display status "Detecting Disk Drives...", and then call a method to read the drives and populate the form with information. I have it working, except when the form loads it calls the method before displaying the label. Therefore it appears to be hung (the label is actually a white box on a gray background). I have tried timers and threads and everything I can think of, each with a different dead end. I have not yet found a way to have the label update before calling the method to read the drives.
The method getAndDisplayData() is wait 'hangs' my program. I would like for it not to be called until after the form has updated the text of lblDisplayStatus.Text
I also do not want the user to have to interact with the form before calling the method.
Here is my C# code:
private void USB_Utility_Load(object sender, EventArgs e)
{
lblDisplayStatus.Text = "Detecting Disk Drives...";
}
private void tabUSB_Prep_Enter(object sender, EventArgs e)
{
tabUSB_Prep.Controls.Clear();
getAndDisplayData();
}
Any help would be greatly appreciated.
Here is the code that I ended up with:
BackgroundWorker _worker;
private void USB_Utility_Load(object sender, EventArgs e)
{
_worker = new BackgroundWorker(); // Should be a field on the form.
_worker.DoWork += DoWork;
_worker.RunWorkerCompleted += RunWorkerCompleted;
lblDisplayStatus.Text = "Detecting Disk Drives...";
_worker.RunWorkerAsync();
}
//Background Worker
private void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
lblDisplayStatus.Text = "Done...";
displayData();
}
private void DoWork(object sender, DoWorkEventArgs e)
{
getData();
}
The old-fashioned way would be to use a BackgroundWorker to run the blocking work in getAndDisplayData and then update the label before starting the worker and again when the worker completes.
Now-adays I assume you could also use tasks to get the exact same result, but I haven't actually tried it as WinForms is not often first choice for new projects.
BackgroundWorker _worker;
public void Form_Load(object sender, EventArgs e) {
_worker = new BackgroundWorker(); // Should be a field on the form.
_worker.DoWork += DoWork;
_worker.RunWorkerCompleted += RunWorkerCompleted;
lblDisplayStatus.Text = "Detecting Disk Drives...";
_worker.RunWorkerAsync();
}
private void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
lblDisplayStatus.Text = "Done...";
}
private void DoWork(object sender, DoWorkEventArgs e) {
getAndDisplayData();
}
About background workers
you can try this
private void USB_Utility_Load(object sender, EventArgs e)
{
lblDisplayStatus.Text = "Detecting Disk Drives...";
}
private void tabUSB_Prep_Enter(object sender, EventArgs e)
{
tabUSB_Prep.Controls.Clear();
Task<List<string>> t = new Task<List<string>>(DetectDrivesMethod());
t.ContinueWith((result)=>DisplayDrives(result.Result),TaskScheduler.FromCurrentSynchronizationContext);
t.Start();
}
You can tweak the code to fit your requirement. In DetectDriveMethod you will have logic to get data in background thread and in continue with, you can have logic to update UI. It is important that you pass syncronization context otherwise you will end up with Cross Thread exceptions.
If you want to use the new(ish) async/await pattern, you need to use the TaskScheduler to update the UI from the original thread. Here's an example:
// clear the form
tabUSB_Prep.Controls.Clear();
// This is just to show crossing a "context" works
string test = "";
// get the UI's current TaskScheduler
var scheduler = TaskScheduler.FromCurrentSynchronizationContext();
// This can be used to wrap a method that doesn't
// directly implement async/await
Task.Run(() =>
{
// Your method to GET the data (don't update the UI here)
test = "I can set a variable in this context!";
}).ContinueWith(task =>
{
if (task.Status == TaskStatus.RanToCompletion)
{
// update your UI here
// Again, this is just to show how crossing the context works
MessageBox.Show(test);
}
else
{
// update UI with an error message, or display a MessageBox?
}
}, scheduler);
I am making and app using C# and Winforms that archives and saves folders to specified locations,for archiving folders i have a BackgroundWorker which takes as input a folder path and generates a zip archive.Now in the next step the file needs to be moved at specified location,again as the file is large enough and could hang up UI thread i moved the code to another BackgroundWorker named FileMove,everything works well except that the FileMove is not reporting any progress,here is the function that i call as soon as archiving is over;
private void FileMove_DoWork(object sender, DoWorkEventArgs e)
{
label3.Text = "Saving file,please wait...";
File.Move(temppath + #"\Output.jpg", savefilename);
}
private void FileMove_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
label3.Text = "Saving file,please wait... " + e.ProgressPercentage.ToString(); //This should show Progress Percentage but it doesn't.
}
private void FileMove_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
label3.Text = ("The folder has been successfully hidden.");
button1.Enabled = true;
button2.Enabled = true;
button3.Enabled = true;
this.ControlBox = true;
}
The problem i'm facing is as soon as file moving starts label3 shows "Saving file,please wait..." and after a long time(as i'm compressing 900-1000 MB)it shows "The folder has been successfully hidden.".During ProgressChanged event label should also show Percentage but it doesn't.Please point out or correct where i've gone wrong.Any help will be appreciated.
First, your BackgroundWorker is trying to update the UI from its background thread, which is a no-no in multithreaded UI apps.
To update the UI you'll need it to switch to the UI thread to do the update. This is done by first checking if the label3.InvokeRequired is true (indicating you can't update the UI from the current thread), then passing a delegate to label3.Invoke (not Delegate.Invoke())
This is a pattern you need to be very familiar with for WinForms development. The Control.Invoke MSDN page includes a sample of leveraging this pattern.
Second, you need to call BackgroundWorker.ReportProgress() periodically, which fires the ProgressChanged event with a percentage-complete value.
Here's a sample app. It assumes you've got a Form with a Button, a Label, and a BackgroundWorker with WorkgerReportsProgress = true (and WorkerSupportsCancellation = true, for bonus points).
When you click the button it starts a 5-second blocking task, then switches to 10 1-second blocking tasks (reporting progress along the way).
Note the helper method InvokeIfRequired() that ensures the UI is updated from the correct thread. There's no harm in using this excessively.
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
if (backgroundWorker1.IsBusy)
{
label1.Text = "Reset!";
backgroundWorker1.CancelAsync();
return;
}
backgroundWorker1.RunWorkerAsync();
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
label1.InvokeIfRequired(() => label1.Text = "Gettin busy");
System.Threading.Thread.Sleep(5000);
for (int i = 0; i < 10; i++)
{
backgroundWorker1.ReportProgress(i*10);
System.Threading.Thread.Sleep(1000);
}
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
label1.InvokeIfRequired(() => label1.Text = "Done");
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
label1.InvokeIfRequired(() => label1.Text = string.Format("{0}% done", e.ProgressPercentage));
}
}
public static class InvokeExtensions
{
public static void InvokeIfRequired(this ISynchronizeInvoke control, MethodInvoker action)
{
if (control.InvokeRequired)
{
control.Invoke(action, null);
}
else
{
action();
}
}
}
private void AddMyScrollEventHandlers()
{
VScrollBar vScrollBar1 = new VScrollBar();
}
private void button1_Click(object sender, EventArgs e)
{
while (true)
{
if (vScrollBar1.Value + 1 < vScrollBar1.Maximum)
{
vScrollBar1.Value = vScrollBar1.Value + 1;
label1.Text = vScrollBar1.Value.ToString();
}
else
{
break;
}
System.Threading.Thread.Sleep(200);
}
}
private void button2_Click(object sender, EventArgs e)
{
// vScrollBar1.Scroll
}
I am new in C#. I was working on scroll. What I wanted here is, if anyone click button1 then scroll automatically move to the end and I wanted to show gradual value in label1. Also when someone click button2 scrolling stop.
Now the problem is label1 do not show gradual change in value. It shows value once when the scrolling stop.
Also when scrolling continue i,e when while loop is working I can not click on button2. Actually I can not click on the form even.
Someone please give me some idea how to do this.
This happens because the thread that is performing the task is busy, and it's the same thread that updates the UI. You can use a multithreading solution. Take a look at
BackgroundWorker
All the UI events run in the main thread of the application, so the application can only process one event at a time. When the application is processing an event, no other event will be processed.
Since you are doing a UI related work periodically, the best option is to use the Timer class:
Drop Timer from the toolbox into the form.
In the properties window, set the interval to 200.
Double click the timer object to create the Tick event handler.
Put this code in the newly created timer1_Tick method:
if (vScrollBar1.Value + 1 < vScrollBar1.Maximum)
{
vScrollBar1.Value = vScrollBar1.Value + 1;
label1.Text = vScrollBar1.Value.ToString();
}
else
{
timer1.Stop();
}
Change your methods as below:
private void AddMyScrollEventHandlers()
{
timer1.Start();
}
private void button2_Click(object sender, EventArgs e)
{
timer1.Stop();
}
Now you're done.
I would recommend using BackgroundWorker control, as suggested by Agustin Meriles. However, one more important thing to note is that You should use Control.Invoke(...) method to update controls from another thread.
I've modified Your code, tested it in a sample application and it seems to work correctly.
First, add a new BackgroundWorker control to Your form and assign backgroundWorker1_DoWork to its DoWork event.
Then, You can use the code below:
private void button1_Click(object sender, EventArgs e)
{
//code from here is moved to BackgroundWorker control
backgroundWorker1.RunWorkerAsync();
}
private void button2_Click(object sender, EventArgs e)
{
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
//while (true)
//the condition directly in the while looks more clear to me
while (vScrollBar1.Value + 1 < vScrollBar1.Maximum)
{
//update controls using Invoke method and anonymous functions
vScrollBar1.Invoke((MethodInvoker)delegate() { vScrollBar1.Value += 1; });
label1.Invoke((MethodInvoker)delegate() { label1.Text = vScrollBar1.Value.ToString(); });
//when called inside BackgroundWorker, this sleeps the background thread,
//so UI should be responsive now
System.Threading.Thread.Sleep(200);
}
}
If You have any problems when using this code, please let me know.
Update
As mentioned in the comments, You could also use ProgressChanged event of the BackgroundWorker. It requires some more changes in the code, but is more suitable in this case. You can find some information about it here: http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.progresschanged.aspx.
If You are not going to add any other code with more processing in the while loop, You can also use Timer control, as suggested by MD.Unicorn in his answer.
I have a winform which have several combo boxes and a gridview.
Initially I am creating the gridview with Rows and Columns and no data filled in with.
The filling data to grid is a long running task which will loop through all rows and read column header and depending on that it will apply different color and data to each cell.
What I am trying to achieve is to load the grid as above in form load event, and after the form loaded start filling data to grid so user can see what happening. Same things apply to the combo box value change since I will load data according to the combo value.
What I have tried is something like this...
In form load I am calling method
private void LoadForm()
{
DataBind(); // this will load the initial grid without cell data
this.BeginInvoke((MethodInvoker)this.LongRunningProcess1);
this.BeginInvoke((MethodInvoker)this.LongRunningProcess2);
}
But still it taking long time and I don't have the responsive UI.
I also tried something like this but no luck....
ThreadStart ts = LongRunningProcess1;
Thread t1 = new Thread(ts);
t1.Start();
Also using a background worker to complete the long running operation causes "Cross thread operation" issue.
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
LongRunningProcess1();
LongRunningProcess2();
}
Any help to make this working is appreciate..
Thanks
UPDATE
I found a really cool solution Updating Your Form from Another Thread without Creating Delegates for Every Type of Update
Thanks for the answers!!!
To avoid the CrossThreadException in the completed-event of the background worker, wrap your callback method like this:
public void WorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (this.InvokeRequired)
{
this.Invoke(new RunWorkerCompletedEventHandler(WorkerCompleted), new {sender, e});
}
else
{
// Business logic goes here
}
}
Typically you will populate the data loaded into the GridView in the else-block. If you on the other hand want to populate the GridView progressively from the long-running background task, you can achieve this with a similar technique using callbacks from the background worker:
public void Worker_DoWork(object sender, DoWorkEventArgs e)
{
foreach (var someParameter in parameterList) // Long-running loop
{
var data = LoadData(someParameter); // Load data for row X
this.Invoke(new Action<object>(UpdateRow),new[]{data}); // Update on UI-thread
}
}
public void UpdateRow(object data)
{
// Code to populate DataGrid row X with data from argument
}
Note that you can call BeginInvoke instead of Invoke if you want to do the UI-updating asynchronously. This will usually not make a difference in this case.
The backgroud worker process is the correct way to go, you just need to eliminate all the "Cross thread operation" exceptions by making sure that all the calls that modify the form elements use the Control.Invoke method wrapper.
If you want to use the backgroundworker/multithreading, you can use delegates updating your form(they run on ui thread). See example here: How to update the GUI from another thread in C#?
Simple example using BackgroundWorker and RunWorkerAsync. Hope this helps.
public partial class Form2 : Form
{
BackgroundWorker worker = new BackgroundWorker();
public Form2()
{
worker.WorkerReportsProgress = true;
worker.WorkerSupportsCancellation = true;
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);
InitializeComponent();
}
void worker_DoWork(object sender, DoWorkEventArgs e)
{
int totalSteps = 5;
for (int i = 1; i <= totalSteps; i++)
{
Thread.Sleep(1000);
worker.ReportProgress(i);
}
}
void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
resultText.Text = "Worker complete";
btnDoWork.Enabled = true;
progressBar1.Visible = false;
}
private void btnDoWork_Click(object sender, EventArgs e)
{
progressBar1.Visible = true;
worker.RunWorkerAsync();
}
}