I hope I described the problem correctly.
In the following code the drive.IsReady takes some time to complete. Prior to this is the command to print the text "Scanning drives..." in the textbox. The text though appears after the foreach() has completed.
Why is this happening and how can I notify the user prior to the long-running task?
public Form1()
{
InitializeComponent();
button1.Click += new System.EventHandler(this.Button1_Click);
}
private void Button1_Click(object sender, EventArgs e)
{
richTextBox1.Text = "Scanning drives, please wait...";
PopulateComboBox();
}
void PopulateComboBox()
{
System.IO.DriveInfo[] drives = System.IO.DriveInfo.GetDrives();
foreach (System.IO.DriveInfo drive in drives)
{
if (drive.IsReady)
{
comboBox1.Items.Add(drive.Name + drive.VolumeLabel);
}
else
{
comboBox1.Items.Add(drive.Name);
}
}
}
These are the minimal changes required to make the slow part of your code (drive.IsReady) run asynchronously. It won't run faster, the intention is just to keep the UI responsive.
private async void Button1_Click(object sender, EventArgs e) // + async
{
richTextBox1.Text = "Scanning drives, please wait...";
await PopulateComboBox(); // + await
}
async Task PopulateComboBox() // async Task instead of void
{
System.IO.DriveInfo[] drives = System.IO.DriveInfo.GetDrives();
foreach (System.IO.DriveInfo drive in drives)
{
if (await Task.Run(() => drive.IsReady)) // + await Task.Run(() => ...)
{
comboBox1.Items.Add(drive.Name + drive.VolumeLabel);
}
else
{
comboBox1.Items.Add(drive.Name);
}
}
}
Related
In my event load of my form , I call a method loadDg:
private void form_Load(object sender, EventArgs e)
{
loadDg();
}
and
private async Task loadDg()
{
pictureLoading.Visible = true;
await Task.Run(() => { string[] datas = db.row("select * from products");
string[] datas2 = db.row("select * from users");
double one = Convert.ToInt32(datas[0]);
label1.Text = one.toString();
//....
});
pictureLoading.Visible = false; //hide gif animation
}
in my code , db.row This method always returns only 1 row ( string array) , but my ui freezes still , i try update UI continuously with async without freeze at startup
There is nothing to prevent your code run asynchronously. pictureLoading will be invisible even before task is completed. You should fix cross-thread problem and logic of the UI as this:
private void form_Load(object sender, EventArgs e)
{
pictureLoading.Visible = true;
loadDg();
}
private async Task loadDg()
{
await Task.Run(() =>
{
string[] datas = db.row("select * from products");
string[] datas2 = db.row("select * from users");
double one = Convert.ToInt32(datas[0]);
label1.BeginInvoke((Action)delegate ()
{
label1.Text = one.toString();
//hide gif animation
pictureLoading.Visible = false;
});
//....
});
}
Unnecessarily jumping between threads/context should be avoided.
This is an with better resource usage:
private async void form_Load(object sender, EventArgs e)
{
pictureLoading.Visible = true;
try
{
label1.Text = await LoadDgAsync();
}
catch
{
// error handling
}
finally
{
pictureLoading.Visible = false;
}
}
private Task<string> LoadDgAsync()
{
return Task.Run(() =>
{
string[] datas = db.row("select * from products");
string[] datas2 = db.row("select * from users");
double one = Convert.ToInt32(datas[0]);
//....
return one.toString();
});
}
You are calling the loadDg() function synchronously.
Unless you await the loadDg() function call (since its return type is Task) and make the form_Load function asynchronous the function call will be synchronous.
The correct way to fix it is...
private async void form_Load(object sender, EventArgs e)
{
await loadDg();
}
I'm working on a WPF application in Visual Studio, I need to download a large file and extract it in my code. Someone recommended that I use background workers, but now when I try to increase the value on my progress bar it doesn't work... Can anyone help?
public void InstallVersion(string version)
{
string location = File.ReadAllText(#"C:\Users\" + Environment.UserName + #"\AppData\Roaming\MidnightFallsLauncher\data\locator.txt");
location = location + #"\Versions\" + version;
if (File.Exists(location + ".zip"))
File.Delete(location + ".zip");
if (Directory.Exists(location))
{
DirectoryInfo di = new DirectoryInfo(location);
foreach (FileInfo file in di.GetFiles())
{
file.Delete();
}
foreach (DirectoryInfo dir in di.GetDirectories())
{
dir.Delete(true);
}
}
if (!myWorker.IsBusy)
{
myWorker.RunWorkerAsync();
}
}
And here is my worker code
public MainWindow()
{
InitializeComponent();
myWorker.DoWork += new DoWorkEventHandler(myWorker_DoWork);
myWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(myWorker_RunWorkerCompleted);
myWorker.ProgressChanged += new ProgressChangedEventHandler(myWorker_ProgressChanged);
myWorker.WorkerReportsProgress = true;
myWorker.WorkerSupportsCancellation = true;
}
protected void myWorker_DoWork(object sender, DoWorkEventArgs e)
{
string location = File.ReadAllText(#"C:\Users\" + Environment.UserName + #"\AppData\Roaming\MidnightFallsLauncher\data\locator.txt");
location = location + #"\Versions\" + Version;
WebClient Client = new WebClient();
string url = "";
string content = "";
string downloadlink = "";
List<string> availibleVersions = new List<string>();
List<string> versionDownload = new List<string>();
url = "https://midnightfalls.glitch.me/versions.html";
content = Client.DownloadString(url);
foreach (string line in content.Split(new string[] { "<br>", "<br />" }, StringSplitOptions.None))
{
if (line.Contains("0"))
{
availibleVersions.Add(line);
}
}
url = "https://midnightfalls.glitch.me/versionslink.html";
content = Client.DownloadString(url);
foreach (string line in content.Split(new string[] { "<br>", "<br />" }, StringSplitOptions.None))
{
if (line.Contains("https"))
{
versionDownload.Add(line);
}
}
for (var i = 0; i < availibleVersions.Count; i++)
{
if (availibleVersions[i] == Version)
{
downloadlink = versionDownload[i];
}
}
Client.DownloadFile(downloadlink, location + ".zip");
ZipFile.ExtractToDirectory(location + ".zip", location);
File.Delete(location + ".zip");
RunGame(Version);
}
protected void myWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
}
protected void myWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.Dispatcher.Invoke(() =>
{
progress.Value += 10;
});
}
Also, while my worker is running, the UI freezes... I'm pretty sure that's not meant to happen.
EDIT:
The UI is now updating but the progress bar still doesnt work...
It looks like the problem is that the main thread is constantly working while the background worker is doing its work:
while (this.myWorker.IsBusy)
{
this.Dispatcher.Invoke(() =>
{
progress.Value += 10;
});
}
means that your main thread is constantly doing stuff while the background job is working, which is why the UI doesn't update.
You need to move the progress update to the background worker (where you could also set a value that actually makes some sense, e.g. to indicate how many of the 'availableVersion's you have downloaded).
Hope that makes sense.
EDIT:
Suppose we'll put all the code directly in the view, so assume we have a progress bar named 'progressBar' and a button named 'btnStart' (which kicks of the backgroundworker).
Here's the codebehind:
private BackgroundWorker worker;
public MainWindow()
{
InitializeComponent();
this.worker = new BackgroundWorker();
this.worker.DoWork += new DoWorkEventHandler(myWorker_DoWork);
this.worker.RunWorkerCompleted += new
RunWorkerCompletedEventHandler(myWorker_RunWorkerCompleted);
this.worker.ProgressChanged += new
ProgressChangedEventHandler(myWorker_ProgressChanged);
this.worker.WorkerReportsProgress = true;
this.worker.WorkerSupportsCancellation = true;
}
private void myWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.progressBar.Value = e.ProgressPercentage;
}
private void myWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// Whatever you need to do when finished here (alert, update a label, etc.)
}
private void myWorker_DoWork(object sender, DoWorkEventArgs e)
{
// Just loop and report new progress. Sleep a little in between each
// progress update so that it isn't over before we have a chance to see it.
for(int i=0;i<100;i++)
{
Thread.Sleep(200);
this.worker.ReportProgress(i);
}
}
private void btnStart_Click(object sender, RoutedEventArgs e)
{
this.worker.RunWorkerAsync();
}
What happens is that the background worker fires an event notifying that progress has changed.
The main thread has a handle on that event, and updates the progress bar.
Since it's a background worker you don't need to use Dispatcher.Invoke - this is already taken care of.
Hope the example clarifies things for you.
I'm pretty sure you're blocking right here:
while (this.myWorker.IsBusy)
{
this.Dispatcher.Invoke(() =>
{
progress.Value += 10;
});
}
You should be calling ReportProgress on your BackgroundWorker instance within your myWorker_DoWork method.
Also, if you're using .NET 4.5 or later, you can dump the BackgroundWorker entirely and rewrite this code using the async/await pattern.
I have a long running method which I made async. I made my button click handler async as well, but when I try to access my label in my button click after the long method is done, it tells me it can't can't access it from another thread. Here is the code:
private void Migrate()
{
for (int i = 2; i <= excelData.GetUpperBound(0); i++)
{
var poco = new ExpandoObject() as IDictionary<string, object>;
foreach (var column in distributionColumnExcelHeaderMappings)
{
if (column.ColumnIndex > 0)
{
var value = excelData[i,column.ColumnIndex]?.ToString();
poco.Add(column.DistributionColumnName.Replace(" ", ""), value);
}
}
pocos.Add(poco);
}
migrationRepository.BulkInsert(insertToTable, "Id", pocos);
}
private async void btnMigrate_Click(object sender, EventArgs e)
{
Task task = new Task(()=> Migrate());
task.Start();
lblStatus.Text = "Migrating data....";
await task;
lblStatus.Text = "Migration Complete";
}
When the button is clicked, I see the status Migrating data..... When that is complete, it throws an error on lblStatus.Text = "Migration Complete". I thought after await, it goes back to the UI thread?
I cleared out most of the code and it still throws the same error. This is a VSTO excel add-in. Could that be part of the problem?
private void Migrate()
{
}
private async void btnMigrate(object sender, EventArgs e)
{
Task.Run(()=>Migrate());
lblStatus.Text = "Done"; //still get error here
}
Try and update your code to the following:
Instead of creating your task and then starting it manually, update it to just await on Task.Run:
private async void btnMigrate_Click(object sender, EventArgs e)
{
lblStatus.Text = "Migrating data....";
await Task.Run(()=> Migrate());
lblStatus.Text = "Migration Complete";
}
Edit:
You can use a helper method that will check to see if the label needs to be invoked before updating.
private async void btnMigrate_Click(object sender, EventArgs e)
{
SetLabelText(lblStatus, "Migrating data....");
await Task.Run(()=> Migrate());
SetLabelText(lblStatus, "Migration complete.");
}
private void SetLabelText(Label label, string text)
{
if (label.InvokeRequired)
{
label.BeginInvoke((MethodInvoker) delegate() {label.Text = text;});
}
else
{
label.Text = text;
}
}
I have created a Windows Forms program that breaks down a file and sends its components to a server. These files are large, so I created a progressBar so users don't think it froze while the transactions are happening. What I would like to do is have some mechanism that will actively trigger only when all threads are complete without blocking the UI thread (again, so the plebs wont think its frozen). The best I could come up with is a kind of passive "wait until true" but I feel like there has to be a better way to do this. I have experimented with trying to create an event or a callback but honestly I've just ended up more confused than when I started. Here is an example of how I am doing this now:
public partial class Program : Form
{
private readonly OpenFileDialog _ofd = new OpenFileDialog();
public delegate void BarDelegate();
private string _path;
private void button1_Click(object sender, EventArgs e)
{
if (_ofd.ShowDialog() != DialogResult.OK) return;
textBox1.Text = _ofd.SafeFileName;
_path = _ofd.FileName;
}
private void button2_Click(object sender, EventArgs e)
{
var allLinesFromFile = File.ReadAllLines(_path);
progressBar1.Minimum = 0;
progressBar1.Maximum = allLinesFromFile.Length;
Task.Factory.StartNew(() => Parallel.ForEach(allLinesFromFile, DoSomething));
while (progressBar1.Value < progressBar1.Maximum) //there has to be a better way to do this...
{
MessageBox.Show("Please wait.", "Record Poster", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
}
//some processes here which should only take place after all threads are complete.
var postingComplete = MessageBox.Show("The posting is complete!", "Record Poster", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
if (postingComplete == DialogResult.OK) Environment.Exit(0);
}
private void DoSomething(string record)
{
//some string manipulation and server transactions here
BeginInvoke(new BarDelegate(() => progressBar1.Increment(1)));
}
}
Try using Microsoft's Reactive Framework (NuGet "System.Reactive.Windows.Forms") for this. Then your code becomes:
private void button2_Click(object sender, EventArgs e)
{
var allLinesFromFile = File.ReadAllLines(_path);
progressBar1.Minimum = 0;
progressBar1.Maximum = allLinesFromFile.Length;
IDisposable subscription =
allLinesFromFile
.ToObservable()
.SelectMany(f => Observable.Start(() => DoSomething(f)))
.ObserveOn(this)
.Do(x => progressBar1.Value += 1)
.Subscribe(x => { }, () =>
{
var postingComplete = MessageBox.Show("The posting is complete!", "Record Poster", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
if (postingComplete == DialogResult.OK)
{
Application.Exit();
}
});
}
private void DoSomething(string record)
{
System.Threading.Thread.Sleep(5);
}
If you need to stop this early then just call subscription.Dispose(). I've tested this and it works fine for me.
You should be using the BackGroundWorker class, see: How to use a BackgroundWorker?
And use BackGroundWorker.RunWorkerComplete for when the thread has finished
Background worker:
**Backgroundworker (System.ComponentModel)**
BackgroundWorker loader = new BackgroundWorker();
loader.DoWork += load_Specials_BW_Thread;
loader.WorkerReportsProgress = true;
loader.ProgressChanged += load_Special_Feeds_Progress_Changed;
private void load_Specials_BW_Thread(object sender, DoWorkEventArgs e)
{
int pctComplete = (int)Math.Floor(ptComplete * 100);//recs done / total recs
(sender as BackgroundWorker).ReportProgress(pctComplete);
}
Good luck!
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.