Develop Reference

Show a Window while application is closing

I've a very heavy application that takes some time to close itself (it also depends on the pc where it is running.. but this is not the matter right now)
I would like to show a custom window with a message during this closing time, but as soon as i call the "Shutdown" method every window disappears (except made for the MessageBox).
This is the code i'm trying to use to achieve my objective
void MainWindow_Closing(object sender, CancelEventArgs e)
{
Task.Factory.StartNew(() =>
{
var closingWaitTest = "application closing, please wait;
Application.Current.Dispatcher.Invoke(() =>
{
var closingSplash = new ClosingSplashWindow(closingWaitTest);
closingSplash.Show();
});
MessageBox.Show(closingWaitTest);
});
Application.Current.Shutdown();
}
I Added a messageBox just to check, and it actually works. I mean, the MessageBox stays open until the application process is alive (i check that from the windows TaskManager) while my Window is instantly closed.
Hope someone can give some advice about this,
thanks in advance (:
EDIT -
So, the main problem is that as soon as i call the Application.Current.Shutdown my splash window instantly closes, while the application process is still up and running for some time (disposing all my things before calling shutdown actually reduced this time a bit).
The point is that i would like to show a window for the entirety of time that the process is still up; given the fact that a MessageBox behaves exactly like that, my question is:
Is there a way to make my ClosingSplashWindow behave like a MessageBox and stay visible until the application process is really dead?

Since Application.Current.Shutdown(); is going to close the application immediately. Maybe you first have a flag to track that application is being closed, cancel the Closing event and initiate the Resource cleanup followed by Application.Current.Shutdown(); again.
The Application_Closing handler may get fired once again, since you've a flag which says you're about to close you can directly exit the handler and all should be good.

First of all, you want to have a flag which indicates that your application is currently shutting down:
private bool IsShuttingDown { get; set; }
Then you should cancel closing operation, perform some heavy work and shut down your application:
private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
if (!IsShuttingDown)
{
e.Cancel = true;
ShowSplashWindow();
PerformHeavyOperation();
Application.Current.Shutdown();
IsShuttingDown = true;
}
}

In the end I solved the problem creating another application that shows a window while the main application process is still up and running.
I know it is not the best way to do it, but i was not able to do it in any other way..
Thank for the support! :)

No Load Complete event for windows form

In windows form on click on Next I need to display other form and start some processing. Am coding in .Net C#
The problem is before the form is complete visible, the method gets triggered and the processing starts and the UI looks like it crashed. Processing started even before controls are loaded. and once processing is done all controls are visible.
The actual output must be all controls should be loaded and then processing must start.
I need to call the method to start processing after the form (user control) is visible and is loaded completely.
I tried this and this, but no luck.
Added code:
private void FeatureRemovalControl_Load(object sender, EventArgs e)
{
pictureBox2.Image = Properties.Resources.line;
prgbar.Value = 0;
//code to load images and some other stuff
StratProcess();
}

You're calling StartProcess (which seems to block until it's finished) from your UI thread. Because WinForms repaints occur on that thread, nothing is painted, and it appears that your process has hung. You should look at using a BackgroundWorker, or other way to call StartProcess asynchronously.

Best way, if you ask me, would be to start processing asynchronously, so that you maintain full control of the UI and process at the same time.
http://msdn.microsoft.com/en-us/library/2e08f6yc(v=vs.71).aspx

Try calling that method at the end of the FormLoad event, the control should have finished loading by then. If it hasn't that you may need perform some checks and possibly create a custom event that fires when you're happy that it is ready.
Another solution is to have a button that the user must press to trigger the processing, which they will only be able to click once everything has loaded
EDIT: The reason it look's like it's happening is because you're starting the process in one of the control's load method, which I assume is not the last control to load, so it's starts processing before the other controls are given a chance to load. Make StratProcess method public and call it in the FormLoad method of the parent form instead, like so:
private void ParentForm_Load(object sender, EventArgs e)
{
FeatureRemovalControl.StratProcess(); // Should it be called StartProcess instead?
}
Beware though this is still doing the processing on the UI thread, so the screen may appear to 'hang' whilst this is happening so I advise you move it to a background thread as others have suggested.

I can only close a form once, InvalidOperation Exception Invoke or BeginInvoke cannot be called on a control until the window handle has been created

Hi
I'm opening a form like this from my main form when the user makes a selection of a menu item.
private void commToolStripMenuItem_Click(object sender, EventArgs e)
{
Command_Form Command_Form1 = new Command_Form();
Command_Form1.ShowDialog();
// Command_Form1.Dispose(); this didn't help
}
Inside the form "Command_Form1"
I close it like this when the user clicks on the close button
private void Close_button_Click(object sender, EventArgs e)
{
this.Close(); //I get the exception here
}
This process works fine once but on the second closing of the form
(Which I hope is a completely different/new instance of the form) I get the error in the title of this post.
This is the output in the debug window.
A first chance exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll
All the topics that list this error go on about not trying to do anything to a form that has not been displayed but this happens when I click on a button in the form.
It would seem to me that pretty much ensures the form has been displayed if I'm able to click its button.
The other posts I've found that list this type of error go on about making thread safe calls so I tried this as an experiment but it didn't make any difference.
private void Close_button_Click(object sender, EventArgs e)
{
if (this.InvokeRequired)
{
CloseCallback d = new CloseCallback(Close_button_Click);
Invoke(d, new object[] { sender, e });
}
else
{
this.Close();
I have multiple threads in my application but they are created by the controls I'm using not by me explicitly.
I am passing data from a serial port to/from the form by Marshling the received/sent data via a delegate[s].
It makes sense that the serial port would run on a different thread than the form but why would a button click on a form be in a diffrent thread than the form????
The whole thread thing is very confuzing
How do I figure out what threads originated where and what is going on in the threads that I didn't create explicitly?
Why would I need to invoke the form's close method via a delegate?
Heck is there anything I can do in this multi threading environment that is thread safe How in do I know if what I'm doing is unsafe/safe if I don't know what/where/why/who/when is creating threads?

My guess is your close() call is not throwing that exception, but something that happens after close(). Have you stepped into the code with the debugger to see when it is fired?
As to when you need to invoke...There is only one thread allowed to make changes and access dynamic properties on the GUI, call it the GUI thread. The GUI thread is responsible for updating layout, firing events like buttons, etc. If you ever access the GUI from another thread (like a timer event) you need to use invoke() to queue your function to be run on the GUI thread. BeginInvoke will also queue the function but is asynchronous (will only queue the function to be run on GUI thread, but will not wait for it to finish).
Close_button_click will only be called by your gui thread when the button click event fires(unless you explicitly call it somewhere else in your code behind, not recommended!), so invokeRequired=false in your code above, and the invoke code is never executed.

How to improve UI in .Net Compact Framework, C#?

I have some WinForms in my application.
On some form , I am loading other forms which have lot of data to show.
So when I click a button to load these forms they take, 9-10 seconds to load,
I wana improve this. I have heard about Background thread but don't know how to use this.
Means on the button click what should i do so that I can see my form imidiately and the processing is done by background thread ?
Please guide me so that I can improve my UI.

Getting the form to show immediately, should be fairly simple and you don't need a background thread to do it.
My guess is that you are retrieving all that data prior to loading the form or you are retrieving the data on the same thread that loads the form. You should be able to call the form with the data it needs to retrieve the rest of the data (such as ID's).
Then you just need to find a way for the data processing to happen on a thread other than the thread that creates the form.
This may not be the most elegant solution, but it gets the job done. It uses a System.Windows.Forms.Timer
private void Form1_Load(object sender, EventArgs e)
{
timer1.Start();
}
private void timer1_Tick(object sender, EventArgs e)
{
timer1.Stop();
//fill controls with data
}
If you have several sets of data that you are retrieving, you may want to consider setting up a queue of tasks to retrieve each set.
Any way that you do it. Make sure to disable any buttons(or other ui) that could cause errors if the data is not loaded.
Edit: It should be noted that winform controls don't always play nice with threads. The nice thing about the System.Windows.Forms.Timer (as opposed to System.Timers.Timer)is that it designed to play nice with controls.

BackgroundWorker are easy to use. Mainly you subscribe to DoWork event, this is where you'd put your work that will be done in a seperate thread. And you also subscribe to RunWorkerCompleted event. This will get raised when your DoWork has completed.
In this method you'd simply bind the data fetched by the DoWork method.
You can use the DoWork eventarg to pass data between DoWork and RunWorkerCompleted.
You can also cancel the work and also the you can use the RunWorkerCompleted eventArg to get the data from the DoWork and also inspect the Error property for exception handling.
IF you have lots of data, you can use a batching process, to get data per batch and display them into your UI. You can show how many total records will be fetch and the progress of it 100 out of 1000 have been loaded, 200 out of 1000 have been loaded etc, to keep the user informed. You could also provide a Cancel option so the user can stop the fetch.
In your button click you'd simply call myBackgroundWorker.RunWorkerAsync().
this will call your DoWork Handler which will be done in a seperate thread not the main UI Thread, so your UI will not FREEZE during the background worker DoWork.
The backgroundworker also support report progress.

If your problem is the main form Freezing, what you need is to collect the data on a separated Thread than the Main form is running.
To achieve that, you can do something like this:
BackgroundWorker worker;
public Form1()
{
InitializeComponent();
worker = new BackgroundWorker();
}
private void button1_Click(object sender, EventArgs e)
{
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerAsync();
}
void worker_DoWork(object sender, DoWorkEventArgs e)
{
//Collect data and open your second form here;
}

Why is Form.Refresh() not working?

I'm running a data import, using a Windows form to kick off the import and show progress.
I've got this whole thing so nice and user friendly, with major and minor progress bars and everything... but just one problem... the form refresh keeps going AWOL.
I have a call to Form.Refresh() every time I update my labels/progress bars, and it usually starts off working. But if ever I need to break into debug mode, just to hand-hold the import a bit, the Refresh() call stops working, and sometimes even if I'm running without Debug mode, at some unpredictable point the same thing happens: the labels and progress bars do not get updated, and if you hide the form and reopen it, the form does not repaint at all - it just shows up entirely white.
Why, oh why, does Form.Refresh() stop working, and how can I fix this?

It sounds as if the import runs on the UI thread, which means that this thread is blocked, preventing the form from repainting itself. A better approach would be to use a BackgroundWorker component, do the import in the DoWork event handler and use the ProgressChanged to update the UI.
Example:
private void StartImport()
{
backgroundWorker.WorkerReportsProgress = true;
backgroundWorker.RunWorkerAsync();
}
private void BackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
// do some work simulating a lenghy process which occasionally
// reports progress with data back to the caller
for (int i = 0; i < 100; i++)
{
Thread.Sleep(200);
backgroundWorker.ReportProgress(i, "Item No " + i.ToString());
}
}
private void BackgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
listBox.Items.Add(e.UserState.ToString());
}
Using this approach you will typically not need to call Refresh to force a repaint of the form.

You may want to change your code into using BeginUpdate and EndUpdate, like so:
Control.BeginUpdate();
// Do something to the control, e.g. add items or whatnot
Control.EndUpdate();
This way Refresh shouldn't be necessary.
AFAIK constantly calling Refresh is really a hack and should be avoiding, as it stresses the CPU quite a bit (it has to refresh everything instead of just the things which are changed).
Edit: If the form starts being white, it seems the drawing code is not been called at all, which indicates it's somewhat not responding.
I'd check the code for anything that can deadlock or otherwisely hang.

You could use observer pattern..in short if anything changes in model observer pattern will make sure that change is visible on form..
google it for some examples..

Depending on what .NET framework you're using, you can use the Task.Run approach:
private void btnShowProgress_Click(object sender, EventArgs e)
{
progressBar1.Value = 0;
Task.Run(() =>
{
for (int i = 0; i <= 100; i++)
{
Thread.Sleep(100);
progressBar1.Invoke(new MethodInvoker(delegate { progressBar1.Value = i; }));
}
});
}
Task.Run info
Using invoke with controls

The solution may not be the best practice but it definitely works for small applications.
In Form1 create a bool to check to see if the form is closed.
public bool formclosed = false
Then in Form2 on the Form Closing Event Handler add
formclosed = true
also in the Form2 after
InitializeComponent();
add
formclosed = false;
In Form1 create a timer.
In the timer1.Tick event handler say
private void timer1_Tick(object sender, EventArgs e)
{
if(formclosed == true)
{
Application.Restart();
}
}
This will restart the application and refresh everything ... I also had my text saved to the Properties.Settings.Default so everytime the application started the default settings would show.

I created an initial version of a Progress control using a BackgroundWorker. The Progress control computed and displayed nice things like Estimated Duration, Estimated Time to Completion. Each statistic was displayed by custom control based on a Label control. The Progress control worked in my production code.
Then I made some changes to the Progress control. I switched from basing my custom statistics controls from Label to Panel. I successfully ran all my tests (using NUnit). Then, I created a Test Windows Forms app. The Progress control successfully worked in the Test Windows Forms app.
When I ran my production Windows app with the updated Progress control it didn't display the statistics.
I tried Thread.Sleep(N), Form.Refresh(). None of those worked to update the statistics.
I eventually called Control.Invalidate() on each Statistic control. The Invalidate caused OnPaint to be called and the control happily updated the display with its specific statistic.
For Each Stat_Obj As Control in Statistics_Controls
Stat_Obj.Invalidate()
Next

You might need to give the window time to redraw itself. I understand you're doing the import in a loop and the loop is running on the main UI thread? Try adding this line to the loop:
Application.DoEvents();