I am working on learning Windows Forms with C# and have a bare bones application. I am trying to close it when the user selects File->Exit. I have an event handler attached to it and I have tried calling Application.Exit(), Application.ExitThread() and just closing the form. Nothing. It stays there. I'm not creating any other threads of any sort either.
Ideas? Thanks.
Have you tried to put a breakpoint in the event handler to see if it is being hit?
If so, the application won't exit if the window messages aren't being delivered (i.e. the UI thread is blocked). One way to test this is to call Environment.Exit() which is more brutal about forcing a close. If this succeeds, you can then figure out why Application.Exit() isn't working.
Application.Exit isn't the normal way to close a GUI application. Use form.Close instead.
private static void OnMenuClose_Click(object sender, System.EventArgs e)
{
Form dlg = ((Control) sender).FindForm();
//dlg.DialogResult = DialogResult.OK;
dlg.Close();
}
Related
I have a published application in C#. Whenever I close the main form by clicking on the red exit button, the form closes but not the whole application. I found this out when I tried shutting down the computer and was subsequently bombarded by lots of child windows with MessageBox alerts I added.
I tried Application.Exit but it still calls all the child windows and alerts. I don't know how to use Environment.Exit and which integer to put into it either.
Also, whenever my forms call the FormClosed or FormClosing event, I close the application with a this.Hide() function; does that affect how my application is behaving?
From MSDN:
Application.Exit
Informs all message pumps that they must terminate, and then closes all application windows after the messages have been processed. This is the code to use if you are have called Application.Run (WinForms applications), this method stops all running message loops on all threads and closes all windows of the application.
Environment.Exit
Terminates this process and gives the underlying operating system the specified exit code. This is the code to call when you are using console application.
This article, Application.Exit vs. Environment.Exit, points towards a good tip:
You can determine if System.Windows.Forms.Application.Run has been called by checking the System.Windows.Forms.Application.MessageLoop property. If true, then Run has been called and you can assume that a WinForms application is executing as follows.
if (System.Windows.Forms.Application.MessageLoop)
{
// WinForms app
System.Windows.Forms.Application.Exit();
}
else
{
// Console app
System.Environment.Exit(1);
}
Reference: Why would Application.Exit fail to work?
I know this is not the problem you had, however another reason this could happen is you have a non background thread open in your application.
using System;
using System.Threading;
using System.Windows.Forms;
namespace Sandbox_Form
{
static class Program
{
private static Thread thread;
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
thread = new Thread(BusyWorkThread);
thread.IsBackground = false;
thread.Start();
Application.Run(new Form());
}
public static void BusyWorkThread()
{
while (true)
{
Thread.Sleep(1000);
}
}
}
}
When IsBackground is false it will keep your program open till the thread completes, if you set IsBackground to true the thread will not keep the program open. Things like BackgroundWoker, ThreadPool, and Task all internally use a thread with IsBackground set to true.
By the way. whenever my forms call the formclosed or form closing event I close the applciation with a this.Hide() function. Does that affect how my application is behaving now?
In short, yes. The entire application will end when the main form (the form started via Application.Run in the Main method) is closed (not hidden).
If your entire application should always fully terminate whenever your main form is closed then you should just remove that form closed handler. By not canceling that event and just letting them form close when the user closes it you will get your desired behavior. As for all of the other forms, if you don't intend to show that same instance of the form again you just just let them close, rather than preventing closure and hiding them. If you are showing them again, then hiding them may be fine.
If you want to be able to have the user click the "x" for your main form, but have another form stay open and, in effect, become the "new" main form, then it's a bit more complicated. In such a case you will need to just hide your main form rather than closing it, but you'll need to add in some sort of mechanism that will actually close the main form when you really do want your app to end. If this is the situation that you're in then you'll need to add more details to your question describing what types of applications should and should not actually end the program.
In this case, the most proper way to exit the application in to override onExit() method in App.xaml.cs:
protected override void OnExit(ExitEventArgs e) {
base.OnExit(e);
}
I have a published application in C#. Whenever I close the main form by clicking on the red exit button, the form closes but not the whole application. I found this out when I tried shutting down the computer and was subsequently bombarded by lots of child windows with MessageBox alerts I added.
I tried Application.Exit but it still calls all the child windows and alerts. I don't know how to use Environment.Exit and which integer to put into it either.
Also, whenever my forms call the FormClosed or FormClosing event, I close the application with a this.Hide() function; does that affect how my application is behaving?
From MSDN:
Application.Exit
Informs all message pumps that they must terminate, and then closes all application windows after the messages have been processed. This is the code to use if you are have called Application.Run (WinForms applications), this method stops all running message loops on all threads and closes all windows of the application.
Environment.Exit
Terminates this process and gives the underlying operating system the specified exit code. This is the code to call when you are using console application.
This article, Application.Exit vs. Environment.Exit, points towards a good tip:
You can determine if System.Windows.Forms.Application.Run has been called by checking the System.Windows.Forms.Application.MessageLoop property. If true, then Run has been called and you can assume that a WinForms application is executing as follows.
if (System.Windows.Forms.Application.MessageLoop)
{
// WinForms app
System.Windows.Forms.Application.Exit();
}
else
{
// Console app
System.Environment.Exit(1);
}
Reference: Why would Application.Exit fail to work?
I know this is not the problem you had, however another reason this could happen is you have a non background thread open in your application.
using System;
using System.Threading;
using System.Windows.Forms;
namespace Sandbox_Form
{
static class Program
{
private static Thread thread;
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
thread = new Thread(BusyWorkThread);
thread.IsBackground = false;
thread.Start();
Application.Run(new Form());
}
public static void BusyWorkThread()
{
while (true)
{
Thread.Sleep(1000);
}
}
}
}
When IsBackground is false it will keep your program open till the thread completes, if you set IsBackground to true the thread will not keep the program open. Things like BackgroundWoker, ThreadPool, and Task all internally use a thread with IsBackground set to true.
By the way. whenever my forms call the formclosed or form closing event I close the applciation with a this.Hide() function. Does that affect how my application is behaving now?
In short, yes. The entire application will end when the main form (the form started via Application.Run in the Main method) is closed (not hidden).
If your entire application should always fully terminate whenever your main form is closed then you should just remove that form closed handler. By not canceling that event and just letting them form close when the user closes it you will get your desired behavior. As for all of the other forms, if you don't intend to show that same instance of the form again you just just let them close, rather than preventing closure and hiding them. If you are showing them again, then hiding them may be fine.
If you want to be able to have the user click the "x" for your main form, but have another form stay open and, in effect, become the "new" main form, then it's a bit more complicated. In such a case you will need to just hide your main form rather than closing it, but you'll need to add in some sort of mechanism that will actually close the main form when you really do want your app to end. If this is the situation that you're in then you'll need to add more details to your question describing what types of applications should and should not actually end the program.
In this case, the most proper way to exit the application in to override onExit() method in App.xaml.cs:
protected override void OnExit(ExitEventArgs e) {
base.OnExit(e);
}
I have a form with a background worker in a c# winforms application (Visual Studio 2010, .net 4). When the background worker is busy I would like to warn the user aboout it when tries to close the form and cancel form closing. I'd like to handle it in form closing event by setting form close cancellation to true.
BUT it still closes the form!
Here is the code snippet I use:
private void FormDrivenDistance_FormClosing(object sender, FormClosingEventArgs e)
{
if (myBackgroundWorker.IsBusy)
{
Messenger.ShowCriticalMessage("Don't close, in progress!");
e.Cancel = true;
}
}
Where is the bug?!
Thanks in advance!
Are you sure that myBackgroundWorker.IsBusy returns true? Have you tried setting a break point inside the check to make sure it's being called?
Are you sure that the event is hooked up properly?
If those things are true, the bug would have to be in some other part of the code.
There may also be some other handler on FormClosing setting Cancel to false, but that's probably a less likely scenario.
What if you move e.Cancel before your message?
Note that if you're trying to prevent the race condition and stop the InvalidOperationException caused when the form closes before the worker completes, it doesn't 100% do so; you might close it in the interval between the completion itself (InProgress is now false) and the callback (OnWorkerCompleted). You still need to handle the exception either way.
Since you have to handle it either way, you may as well just let the user close the form. It's a nuisance for the user to have to wait for something to complete that they don't care about.
I have a form in a Windows form application that I want to display on top of a main form, close it, and then immediately show a dialog box using MessageBox.Show(). But the first form is still showing when the message box is shown, and it does not disappear until I click OK on the message box. I tried waiting to show the message box in an event handler for the form's VisibleChanged event and even calling Refresh() on both the form and the main form. Is there a way I can determine when the first form has fully disappeared before displaying the message box?
Edit:
Here is some code that demonstrates how the forms are being shown.
static class Program
{
// The main form is shown like this:
static void Main()
{
Application.Run(new MainForm());
}
}
public class Class1
{
// _modalForm is the first form that is displayed that won't fully go away
// when it is closed.
ModalForm _modalForm;
BackgroundWorker _worker;
public Class1()
{
_modalForm = new ModalForm();
_worker = new BackGroundWorker();
_worker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted
}
public void Method1()
{
_worker.RunWorkerAsync();
// The first form is shown.
_modalForm.ShowDialog();
}
// This code runs in the UI thread.
void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
_modalForm.VisibleChanged += new EventHandler(_modalForm_visibleChanged);
_modalForm.Close();
}
void _modalForm_visibleChanged(object sender, EventArgs e)
{
// When the message box is shown, the other form is still visible
// and remains so until I click OK.
MessageBox.Show("The other form was just closed.");
// Note: I originally tried to use the FormClosed event instead of
// VisibleChanged. Then I tried Deactivate, in attempt to use an event
// that occurred later thinking that might do the trick. VisibleChanged
// is the latest event that I found.
//
}
I'll guess that you are running your code on Windows XP or Vista/Win7 with Aero turned off. Closing a form does not make the pixels on the screen disappear instantly. The Windows window manager sees that the window for the form got destroyed and that this revealed parts of other windows underneath it. It will deliver a WM_PAINT message to let them know that they need to repaint the parts of the window that got revealed.
This will not work properly if one or more of those windows isn't actively pumping a message loop. They can't see the WM_PAINT message. They won't repaint themselves, the pixels of the closed form will remain on the screen.
Find out why these windows are not responding. Hopefully it is your window and the debugger can show you what the UI thread is doing. Make sure it isn't blocking on something or stuck in a loop.
After seeing the edit: there's indeed blocking going on, of a different kind. The MessageBox.Show() call is modal, it prevents the VisibleChanged event from completing. That delays the closing of the form.
Use System.Diagnostics.Debug.WriteLine() or Console.WriteLine() to get diagnostics in a Window Forms app. You'll see it in the Output window. Or simply use a debugger breakpoint.
The Form.FormClosed event is raised when the form completes closing. At this point, all Form.FormClosing event handlers have been run, and none of them canceled the close.
Form.FormClosed replaced Form.Closed (which is deprecated) in the .NET 2.0 framework.
Form.Closed Event
http://msdn.microsoft.com/en-us/library/system.windows.forms.form.closed(VS.71).aspx
I'm writing a Windows Forms Application in C#.NET
On startup, the application displays a splash screen which is running in a separate thread. Whilst the splash screen is showing, the main application is initialising.
Once the main application has finished initialising, the main form of the application is displayed, and the splash screen still shows over the top.
Everything so far is as expected.
Then, the Splash screen is closed, which causes that thread to exit. For some reason, at the point, the main application windows gets sent behind all other open Windows, notably the Windows Explorer window where you clicked the .exe file to run the application in the first place!
What could be causing the windows to suddenly jump "behind" like this?
Try calling .Activate() on your main window when your thread closes.
It's never been active, and thus has low Z-Order, so whatever is higher will naturally be above it. I had to fix this exact scenario in our app.
Don't forget! You may need to marshal the call to the correct thread using an Invoke()!
I've had this happen at times too. Bob's response is the easiest and works for me in the majority of cases. However, there have been some times where I need to use brute force. Do this via interop like this:
[DllImport("user32.dll")]
public static extern bool SetForegroundWindow(IntPtr hWnd);
Is the splash screen a Modal dialog?
I have seen this window 'jumping' if you dismiss a Modal dialog twice by setting both DialogResult and calling Hide() or close().
Code like this:
private void button1_Click(object sender, System.EventArgs e)
{
this.DialogResult = DialogResult.Abort;
this.Hide();
}
See this blog entry for all of the cases...
You can use code like this :
private void button1_Click(object sender, System.EventArgs e)
{
this.DialogResult = DialogResult.Abort;
this.Hide();
}
Thanks all!