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C# Writing to file hangs UI even when using await Task

I'm trying to save a rather large text file when the user hits the save button. It can be up to 30MBs. After pressing the button, I'd like the texbox to display "Saving..." as it's saving the file and when it completes, display "Saved". However I can't get this to work. I've tried using Task.run, await task.Run, and using a background worker. All these options hang the UI until the save completes. The textbox does not display "Saving..." until after it saves and the program is unresponsive until then. How can I fix this?
private async void btnSave_Click(object sender, RoutedEventArgs e)
{
SaveFileDialog saveFileDialog1 = new SaveFileDialog();
saveFileDialog1.ShowDialog();
// If the file name is not an empty string open it for saving.
if (saveFileDialog1.FileName != "")
{
logFileName = saveFileDialog1.FileName;
btnOpenFile.IsEnabled = false;
btnSave.IsEnabled = false;
tbText1.Text += "\n\n***Saving...***\n";
tbText1.ScrollToEnd();
await Task.Run(() => File.WriteAllText(logFileName, Results.ToString()));
tbText1.Text += "\n\n***SAVED***\n\n";
tbText1.ScrollToEnd();
btnOpenFile.IsEnabled = true;
btnSave.IsEnabled = true;
}

As discussed in the comments, the problem is with Results.ToString().
I tried to reproduce the issue with this code:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
for (int i = 1; i < 40536; i++)
{
stringBuilder.Append(new string('a', i));
}
}
readonly StringBuilder stringBuilder = new StringBuilder();
int tickNumber = 0;
private void sync_Click(object sender, EventArgs e)
{
button1.Enabled = false;
stringBuilder.ToString();
button1.Enabled = true;
}
private async void async_Click(object sender, EventArgs e)
{
button2.Enabled = false;
await Task.Run(() => stringBuilder.ToString());
button2.Enabled = true;
}
private void timer1_Tick(object sender, EventArgs e)
{
tickNumber %= 50;
tickNumber++;
label1.Text = new string('.', tickNumber);
}
}
But it works as expected:
Sometimes UI hands for a little bit though. Is this what are you talking about?
Try moving code that generates contents for StringBuilder inside the task (so this StringBuilder only exists in background thread)

C# BackgroundWorker ProgressChanged doesn't get fired until end of function

I have a method in my class that has some loops inside.
Main purpose of this method is converting some files so I put a progressbar in my form that should get updated after each file has been converted.
I tried every possible combination and I read everything I could but I couldn't solve this issue.
void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
converterProgressBar.Value = e.ProgressPercentage;
}
is called only after the main loop of my method has been executed.
This is my method:
public string Convert()
{
convertBtn.Enabled = false;
bw.WorkerReportsProgress = true;
bw.WorkerSupportsCancellation = true;
bw.DoWork += new DoWorkEventHandler(bw_DoWork);
bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged);
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
totalCount = files.length;
bw.RunWorkerAsync();
if (!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
foreach (string file in files)
{
countFile++;
if (chk.Checked)
{
class1.DoJob();
}
using (// some code))
{
using (//some other code))
{
try
{
using (// again some code)
{
// job executing
}
}
catch (exception
{
}
}
}
convertedVideosL.Text = txtToUpdate;
convertedVideosL.Refresh();
}
countFile = countFile + 1;
MessageBox.Show("Done");
countFile = -1;
return outputFile;
}
And here are the BackgroundWorker Event Handlers:
void bw_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i <= totalCount; i++)
{
if (bw.CancellationPending)
{
e.Cancel = true;
}
else
{
int progress = Convert.ToInt32(i * 100 / totalCount);
(sender as BackgroundWorker).ReportProgress(progress, i);
}
}
}
void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
converterProgressBar.Value = e.ProgressPercentage;
}
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Cancelled == false)
{
convertedVideosL.Text = "Finished!";
}
else
{
convertedVideosL.Text = "Operation has been cancelled!";
}
}
But I cannot get to update the progress bar for every file that is converted.
It waits for the foreach loop to end and then calls bw_ProgressChanged.
If I put RunWorkerAsync() inside the foreach loop an exception is thrown that says the BackgroundWorker is busy and cannot execute other tasks.
It seems to me obvious that DoWork() only executes a for loop then it shouldn't be aware of the conversion going on but ProgressChanged should be fired by ReportProgress(progress,i).
Could please someone explain me why and help me with a solution?
Thanks!

Currently the conversion is not executed by the instance of the BackgroundWorker type. The conversion should be called from the DoWork event handler.
Please consider extracting the conversion-related functionality:
if (!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
foreach (string file in files)
{
// Details...
}
into the separate method. After that just call the method from the DoWork event handler.
Pseudo-code to demonstrate the idea:
public void StartConversion()
{
...
TWorkerArgument workerArgument = ...;
worker.RunWorkerAsync(workerArgument);
// No message box here because of asynchronous execution (please see below).
}
private void BackgroundWorkerDoWork(object sender, DoWorkEventArgs e)
{
// Get the BackgroundWorker that raised this event.
BackgroundWorker worker = sender as BackgroundWorker;
e.Result = Convert(worker, (TWorkerArgument)e.Argument);
}
private static TWorkerResult Convert(BackgroundWorker worker, TWorkerArgument workerArgument)
{
if (!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
foreach (string file in files)
{
// Details...
worker.ReportProgress(percentComplete);
}
return ...;
}
private void BackgroundWorkerRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// Show the message box here if required.
}
Please replace the TWorkerArgument and TWorkerResult types appropriately.
Also, please refer to the example which uses the BackgroundWorker class for the additional details: How to: Implement a Form That Uses a Background Operation, MSDN.

Background Worker to populate combobox in windows form application

I want to implement background worker in my windows application.
Currently I am using button event handler to load the combo box with data. As the query hangs the user interface, i would like to implement background worker as that the query runs in different thread. I have never used this background worker in any of my application. I did some research on this and still unable to implement this. Any help or advice will be greatly appreciated.
This is how my button event handler looks like
private void button6_Click(object sender, EventArgs e)
{
if (comboBox1.SelectedItem.ToString() == "All")
{
findAllUser();
}
else
{
//Do Something!!!
}
}
findAllUser() will fetch all the user from active directory which normally takes time and makes the UI unresponsive. Code for findAllUser() looks like this.
public void findAllUser()
{
System.DirectoryServices.DirectoryEntry entry = new System.DirectoryServices.DirectoryEntry("LDAP://DC=xyz, DC=com");
System.DirectoryServices.DirectorySearcher mySearcher = new System.DirectoryServices.DirectorySearcher(entry);
mySearcher.Filter = "(&(objectClass=user))";
foreach (System.DirectoryServices.SearchResult resEnt in mySearcher.FindAll())
{
try
{
System.DirectoryServices.DirectoryEntry de = resEnt.GetDirectoryEntry();
comboBox2.Items.Add(de.Properties["GivenName"].Value.ToString() + " " + de.Properties["sn"].Value.ToString() + " " + "[" + de.Properties["sAMAccountName"].Value.ToString() + "]");
}
catch (Exception)
{
// MessageBox.Show(e.ToString());
}
}
}
Below is how the background worker looks now..all empty
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
}
Any advice how can i implement the code above so that the background worker will populate the combobox2 with the active directory user list.

The easiest way would be to have your findAllUser method build a list of items that need to be added to the combo box, and then have the RunWorkerCompleted method populate the combo box. For example, modify your findAllUser like this:
private List<string> items;
public void findAllUser()
{
items = new List<string>();
System.DirectoryServices.DirectoryEntry entry =
new System.DirectoryServices.DirectoryEntry("LDAP://DC=xyz, DC=com");
System.DirectoryServices.DirectorySearcher mySearcher =
new System.DirectoryServices.DirectorySearcher(entry);
mySearcher.Filter = "(&(objectClass=user))";
foreach (System.DirectoryServices.SearchResult resEnt in mySearcher.FindAll())
{
try
{
System.DirectoryServices.DirectoryEntry de = resEnt.GetDirectoryEntry();
items.Add(de.Properties["GivenName"].Value.ToString() + " " +
de.Properties["sn"].Value.ToString() + " " + "[" +
de.Properties["sAMAccountName"].Value.ToString() + "]");
}
catch (Exception)
{
// MessageBox.Show(e.ToString());
}
}
}
Then, have your DoWork call findAllUser to do the actual work.
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
findAllUser();
}
And finally, have your RunWorkerCompleted populate the combo box:
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
foreach (var item in items)
{
comboBox2.Items.Add(item);
}
}
If you want to show progress, then you need to call ReportProgress from time to time while the worker is doing its business. Since you don't know exactly how long the process will take or exactly how many users it will find, you can't really report accurate progress. In that case, you have to guess. Since you say it takes "like 30 seconds," then you can use that as the 100% mark. So you start a StopWatch when the worker starts its processing, and update every half second or so. Modify your findAllUser function like this:
public void findAllUser()
{
const int ExpectedTime = 30000; // 30,000 milliseconds
// stopwatch keeps track of elapsed time
Stopwatch sw = Stopwatch.StartNew();
// Create a timer that reports progress at 500 ms intervals
System.Timers.Timer UpdateTimer;
UpdateTimer = new System.Threading.Timer(
null,
{
var percentComplete = (100 * sw.ElapsedMilliseconds) / ExpectedTime;
if (percentComplete > 100) percentComplete = 100;
ReportProgress(percentComplete);
// Update again in 500 ms if not already at max
if (percentComplete < 100)
UpdateTimer.Change(500, Timeout.Infinite);
}, 500, Timeout.Infinite);
items = new List<string>();
// rest of findAllUser here
// dispose of the timer.
UpdateTimer.Dispose();
}
And then, in your ProgressChanged event handler, update your progress bar.
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
// Update the progress bar with the value from e.ProgressPercentage
}
Again, because you don't know exactly how long things are going to take, you make an estimate. Above, I estimated 30 seconds, and the code blindly assumes that if 15 seconds have gone by, then it's half done.
Note that I create the timer as a one-shot and re-initialize it after every tick. I do this because I want to prevent concurrent updates. The timer fires on a separate thread, and the ReportProgress method marshals the call to the ProgressChanged event to the UI thread. If the UI thread is busy with other things, then another timer event could come in and you could end up with a bunch of threads all trying to marshal calls to the UI. Probably not a problem in this case because we're only talking a maximum of 60 calls (two calls per second for 30 seconds), but in general it's a good idea to prevent that kind of thing from happening.

Place your code on the backgroundWorker1_DoWork. But I suggest you either use Thread or Task Parallel Library
If you're on .NET 4.0, use the TPL.
You can do it like this:
Task runner = new Task(() =>
{
// do process here
});
runner.Start();
of if you're on older frameworks, use the Thread like this.
Thread thread = new Thread(() =>
{
// do process here
});
thread.IsBackground = true;
thread.Start();
read more about the TPL and Thread.

Using BackgroundWorker is convenient because it automagically invokes the ProgressChanged and RunworkerCompleted event handlers in the UI thread. You can use it like below.
private void AddItem(DirectoryEntry de)
{
comboBox2.Items.Add(de.Properties["GivenName"].Value.ToString() + " " + de.Properties["sn"].Value.ToString() + " " + "[" + de.Properties["sAMAccountName"].Value.ToString() + "]");
}
private void button6_Click(object sender, EventArgs e)
{
if (comboBox1.SelectedItem.ToString() == "All")
{
this.backgroundWorker1.RunWorkerAsync();
}
else
{
//Do Something!!!
}
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
// Bind to the users container.
DirectoryEntry entry = new DirectoryEntry("LDAP://CN=xyz,DC=com");
// Create a DirectorySearcher object.
DirectorySearcher mySearcher = new DirectorySearcher(entry);
try
{
// Create a SearchResultCollection object to hold a collection of SearchResults
// returned by the FindAll method.
SearchResultCollection result = mySearcher.FindAll();
int count = result.Count;
for(int i = 0; i < count; i++)
{
SearchResult resEnt = result[i];
try
{
DirectoryEntry de = resEnt.GetDirectoryEntry();
BeginInvoke(new Action<DirectoryEntry>(AddItem), de);
}
catch (Exception)
{
// MessageBox.Show(e.ToString());
}
this.backgroundWorker1.ReportProgress(i / count);
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.progressBar1.Value = e.ProgressPercentage;
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
this.progressBar1.Value = 100;
}

You can use below logic to implement background worker for your code.
var startListenerWorker = new BackgroundWorker();
startListenerWorker.DoWork += new DoWorkEventHandler(this.StartListenerDoWork);
startListenerWorker.RunWorkerAsync();
private void StartListenerDoWork(object sender, DoWorkEventArgs doWorkEventArgs)
{
// Your logic to load comboBox will go here for running your query
}
you can also implement thread to have your logic run on a separate thread.

Using Backgroundworker with a Timer

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.

Making sure a backgroundworker has finished before running it (again)

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.