I am downloading data after every 5mins using web client but sometimes it shows a concurrency error.
TimerCallback call = down;
temp = new Timer(call);
temp.Change(1000, System.Threading.Timeout.Infinite);
public void down(object obj)
{
if(webflag == true)
webClient.DownloadStringAsync(new Uri(url));
webflag = false;
}
private void FeedsDownloaded(object sender, DownloadStringCompletedEventArgs e)
{
if (e.Error == null)
{
// some processing
}
webflag = true;
temp.Change(5000, System.Threading.Timeout.Infinite);
}
I am beginner so the above code must look pretty messed up. Appreciate guidance, Thanks!
Thank You Drew Marsh, The solution was using webClient.isbusy flag.
if(webClient.isbusy == false)
webClient.DownloadStringAsync(new Uri(url));
Related
I'm getting this exception
The process cannot access the file 'myfile.zip' because it is being used by another process.
When I try to delete a file. I understand the error, but I'm not sure what other process could be using the file.
I'm downloading the file via WebClient asynchronously, but I cancel the download before trying to delete it, which means that process should relinquish it, no?
Here are the relevant methods. It's a simple file-downloader:
private void textBox1_KeyUp(object sender, KeyEventArgs e)
{
string downloadFile = textBox1.Text.Trim();
if (e.Key == Key.Return && downloadFile != "")
{
var dlg = new SaveFileDialog();
dlg.FileName = Path.GetFileName(downloadFile);
dlg.DefaultExt = Path.GetExtension(downloadFile);
var result = dlg.ShowDialog();
if(result.Value)
{
textBox1.Text = "";
textBox1.Focus();
_saveFile = dlg.FileName;
progressBar1.Dispatcher.Invoke(DispatcherPriority.Normal, new Action(() => progressBar1.Foreground = new SolidColorBrush(Color.FromRgb(0, 255, 0))));
_webClient.DownloadFileAsync(new Uri(downloadFile), _saveFile);
}
}
}
private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
if (_webClient.IsBusy && _saveFile != null)
{
var result = MessageBox.Show("Download in progress. Are you sure you want to exit?", "Exit?", MessageBoxButton.YesNo, MessageBoxImage.Warning);
if (result == MessageBoxResult.Yes)
{
_webClient.CancelAsync();
File.Delete(_saveFile);
}
else
{
e.Cancel = true;
}
}
}
You need to wait when downloading realy canceled. When call _webClient.CancelAsync(); next operator executes immediatley before webClient canceled.
May be you need delete the file in callback of CancelAsync(...)
This is my service which checks username and password
[OperationContract]
public bool LoginCheck(string username, string password)
{
RoadTransDataContext db = new RoadTransDataContext();
var _Pass = (from d in db.users where d.username == username select d.password).SingleOrDefault();
if (_Pass == password)
{
return true;
}
else
{
return false;
}
}
And this is child window
private void LoginCheckCompleted(object sender, ServiceReference.LoginCheckCompletedEventArgs e)
{
_Log = e.Result;
}
private void OKButton_Click(object sender, RoutedEventArgs e)
{
ServiceReference.ServiceClient webservice = new ServiceReference.ServiceClient();
webservice.LoginCheckCompleted += new EventHandler<ServiceReference.LoginCheckCompletedEventArgs>(LoginCheckCompleted);
webservice.LoginCheckAsync(txtUserName.Text, txtPassword.Password);
if (_Log == true)
{
this.DialogResult = true;
this.Close();
}
}
problem is that LoginCheckCompleted method is calling when OKButton_Click method finished. so if it input correct username, pass and press button it doing nothing if i click onece again window closing
Silverlight uses the async model of invoking web services and it takes some time to wait until the response is returned. In your example the assigment _Log = e.Result; will be called, let's assume, after 1-2 seconds, whereas the check if (_Log == true) will be called immideately and of course before the assignment.
That's why you should put all the necessary code in the callback and remove all the code after the async call. I've fixed it for you:
private void LoginCheckCompleted(object sender, ServiceReference.LoginCheckCompletedEventArgs e)
{
_Log = e.Result;
if (_Log == true)
{
this.DialogResult = true;
this.Close();
}
}
private void OKButton_Click(object sender, RoutedEventArgs e)
{
ServiceReference.ServiceClient webservice = new ServiceReference.ServiceClient();
webservice.LoginCheckCompleted += new EventHandler<ServiceReference.LoginCheckCompletedEventArgs>(LoginCheckCompleted);
webservice.LoginCheckAsync(txtUserName.Text, txtPassword.Password);
}
i have the pretty same sample as mentioned here.
Fast concluded: MainWindow closes when the last childwindow is closed.
My Problem: I couldn't solve my problems with the described solutions. I can't produce a program where it als takes place. Only in one of my bigger progs. Maybe someone has an idea or knows any further steps.
Thanks for reading - Thomas
As requested here's a bit of code:
This is the part in the MainWindow:
bool editAfterSearch = false;
Movie selectedMovie = (Movie)this.listView.SelectedItem;
Movie backup = (Movie)selectedMovie.Clone();
if (new OnlineSearchWindow().EditMovieViaOnlineSearch(ref selectedMovie, out editAfterSearch))
{
this.coverFlow.Update(selectedMovie);
}
And that's the part of the ChildWindow:
public bool EditMovieViaOnlineSearch(ref Movie preset, out bool editAfter)
{
this.exitWithOk = false;
this.editMovieAfterSearch = false;
this.tbx_SearchTerm.Text = preset.Title;
this.linkedMovie = preset;
this.ShowDialog();
editAfter = editMovieAfterSearch;
if (this.exitWithOk)
{
this.linkedMovie.CloneOnlineInformation(ref preset);
preset.Bitmap = this.linkedMovie.Bitmap;
return true;
}
else
{
return false;
}
}
Try playing with the ShutDownMode property of your App.xaml.cs. The 3 values are OnMainWindowClose, OnLastWindowClose, and OnExplicitShutdown, and the default is OnLastWindowClose
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
this.ShutdownMode = System.Windows.ShutdownMode.OnMainWindowClose;
}
}
The below code worked for me.
private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
if (MessageBoxResult.No == (MessageBox.Show("Are you sure you want to close this?.", "ProjectName", MessageBoxButton.YesNo)))
{
e.Cancel = true;
foreach (var item in Application.Current.Windows)
{
Window window = item as Window;
if (window.Title == "PopUpWindowName")
{
window.Topmost = true;
break;
}
}
return;
}
else
{
base.OnClosed(e);
Application.Current.Shutdown();
}
}
you can try setting the child window's allowShutDown to false and then show the mainwindow. I'm assuming you will start with mainwindow's visibility set to hidden.
Application.Current.MainWindow.Visibility = System.Windows.Visibility.Visible;
this.allowShutDown = false;
The allowShutDown will be your own property which u can set to enable you have to handle the closing event.
Greetings,
I want to write code that executes within an event handler, inside a WPF Windows application, that can detect a keypress, specifically an "Escape" character keypress, within a processing loop. This will allow the user to escape from processing. I realize this may be accomplished with some kind of multi-threaded approach, but the problem seems so simple I wondered if it might be accomplished as follows:
// Attempt 1: See if Keyboard static IsKeyDown method detects key presses while executing.
// Note that this was not successful. The Keyboard states do not appear to be updated during processing.
bool iskeypressed = false;
while (!iskeypressed)
{
System.Threading.Thread.Sleep(1000);
if (Keyboard.IsKeyDown(Key.Enter))
iskeypressed = true;
}
So, on to attempt #2. I saw some articles and samples using the Pinvoke "GetKeyboardState" method. I'm not sure I used the method correctly, but here is my attempt. It is a bit clumsy to refer to a Windows.Forms enumeration in a WPF application, but it seems like it could work.
// Attempt 2: Use Pinvoke GetKeyboardState method.
// So far, I've been unsuccessful with this as well, but I'm not sure my usage is correct.
bool iskeypressed = false;
while (!iskeypressed)
{
System.Threading.Thread.Sleep(1000);
if (isEscapePressed())
iskeypressed = true;
}
}
[DllImport("user32.dll")] public static extern int GetKeyboardState(byte[] lpKeyState);
private bool isEscapePressed()
{
byte[] keyboardState = new byte[255];
int keystate = GetKeyboardState(keyboardState);
if (keyboardState[(int)System.Windows.Forms.Keys.Escape] == 128)
return true;
else
return false;
}
But unfortunately, I'm not seeing any change in the keyboard states as this executes. I also played around a little with calls to the Dispatcher to see if I could get the keyboard information to refresh during processing, but I have not been successful with any technique.
I'm out of ideas. Can someone propose something? Thank you in advance for your assistance.
David
Something like this:
private bool IsCancelled { get; set; }
private void OnButtonClick(object sender, EventArgs e)
{
Action doWorkDelegate = DoWork;
doWorkDelegate.BeginInvoke(null, null);
}
protected override void OnKeyDown(KeyEventArgs e) {
if (e.Key == Key.Escape) {
IsCancelled = true;
e.Handled = true;
} else {
base.OnKeyDown(e);
}
}
private void DoWork()
{
IsCancelled = false;
while (!IsCancelled)
{
System.Threading.Thread.Sleep(1000);
}
}
The important point is that the method that does the work is executed in a separate thread so the main thread can process user input (key strokes).
You can not detect a key event while you are blocking WPF by executing a very long loop. You must use a multithreaded approach or you have to split the loop.
Using a BackgroundWorker is an easy way to let WPF continue handling the frontend while executing the loop.
private BackgroundWorker bw;
private void Button_Click(object sender, RoutedEventArgs e)
{
if (bw != null)
return;
bw = new BackgroundWorker();
bw.WorkerSupportsCancellation = true;
bw.WorkerReportsProgress = true;
bw.DoWork += (senderBw, eBw) =>
{
for (int i = 0; i < 100; i++)
{
Thread.Sleep(1000);
bw.ReportProgress(i);
if (eBw.Cancel)
return;
}
};
bw.ProgressChanged += (senderBw, eBw) =>
{
//TODO set progressbar to eBw.ProgressPercentage
};
bw.RunWorkerCompleted += (senderBw, eBw) =>
{
this.bw = null;
//TODO frontend stuff (hide progressbar etc)
};
bw.RunWorkerAsync();
}
private void MainWindow_KeyDown(object sender, KeyEventArgs e)
{
if (this.bw != null && this.bw.IsBusy && e.Key == Key.Escape)
this.bw.CancelAsync();
}
Trying to implement drag and drop between 2 listboxes and all examples I've seen so far don't really smell good.
Can someone point me to or show me a good implementation?
Here's a sample form. Get started with a new WF project and drop two list boxes on the form. Make the code look like this:
public partial class Form1 : Form {
public Form1() {
InitializeComponent();
listBox1.Items.AddRange(new object[] { "one", "two", "three" });
listBox1.MouseDown += new MouseEventHandler(listBox1_MouseDown);
listBox1.MouseMove += new MouseEventHandler(listBox1_MouseMove);
listBox2.AllowDrop = true;
listBox2.DragEnter += new DragEventHandler(listBox2_DragEnter);
listBox2.DragDrop += new DragEventHandler(listBox2_DragDrop);
}
private Point mDownPos;
void listBox1_MouseDown(object sender, MouseEventArgs e) {
mDownPos = e.Location;
}
void listBox1_MouseMove(object sender, MouseEventArgs e) {
if (e.Button != MouseButtons.Left) return;
int index = listBox1.IndexFromPoint(e.Location);
if (index < 0) return;
if (Math.Abs(e.X - mDownPos.X) >= SystemInformation.DragSize.Width ||
Math.Abs(e.Y - mDownPos.Y) >= SystemInformation.DragSize.Height)
DoDragDrop(new DragObject(listBox1, listBox1.Items[index]), DragDropEffects.Move);
}
void listBox2_DragEnter(object sender, DragEventArgs e) {
DragObject obj = e.Data.GetData(typeof(DragObject)) as DragObject;
if (obj != null && obj.source != listBox2) e.Effect = e.AllowedEffect;
}
void listBox2_DragDrop(object sender, DragEventArgs e) {
DragObject obj = e.Data.GetData(typeof(DragObject)) as DragObject;
listBox2.Items.Add(obj.item);
obj.source.Items.Remove(obj.item);
}
private class DragObject {
public ListBox source;
public object item;
public DragObject(ListBox box, object data) { source = box; item = data; }
}
}
the proper way to do a drag-drop control in .net is by running code in the 2nd control's DragDrop event handler.
It may "smell" weird, but this is how it works in .NET.
Google gave this: http://www.codeproject.com/KB/dotnet/csdragndrop01.aspx
It seems a pretty reasonable tutorial. If it smells bad, I think that's more to do with the API for drag and drop being awkward to use rather than the tutorial itself being poor.