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In my Windows form the application doesn't exit even though I execute this.Close();
private void exitButton_Click(object sender, EventArgs e)
{
this.Close();
}
If I try disposing it directly it just crashes.
In my main class I open an instance, which is what i'm trying to close. Before it didnt't want to close, it didn't open.
This is not my main class.
FIX: Replacing "show()" with "showDialog()" fixed it.
Remarks from Form.Close()
When a form is closed, all resources created within the object are
closed and the form is disposed. You can prevent the closing of a form
at run time by handling the Closing event and setting the Cancel
property of the CancelEventArgs passed as a parameter to your event
handler. If the form you are closing is the startup form of your
application, your application ends.
The two conditions when a form is not disposed on Close is when (1) it
is part of a multiple-document interface (MDI) application, and the
form is not visible; and (2) you have displayed the form using
ShowDialog. In these cases, you will need to call Dispose manually to
mark all of the form's controls for garbage collection. NoteNote
When the Close method is called on a Form displayed as a modeless
window, you cannot call the Show method to make the form visible,
because the form's resources have already been released. To hide a
form and then make it visible, use the Control.Hide method. Caution
noteCaution
Prior to the .NET Framework 2.0, the Form.Closed and Form.Closing
events are not raised when the Application.Exit method is called to
exit your application. If you have validation code in either of these
events that must be executed, you should call the Form.Close method
for each open form individually before calling the Exit method.
This clearly states that the form should close and application should end unless you do something else we cannot see in your example.
The Close method is a Form's method, it closes the Form, this closes the Application instead :
// Close everything down.
Application.Exit();
As you can see the Application Class doesn't have a Close method, it has an Exit method instead, the this.Close() closes the concerned Form, but keeps the application running.
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);
}
This question already has answers here:
How do I prevent the app from terminating when I close the startup form?
(4 answers)
Closed 7 years ago.
well, i did a multi forms app in c#. This means that i had more forms including one which is the main menu. All forms has ,among others,a button which return to the main menu.(Except from the main menu form which has buttons which access a specific form)
Well this is how i make this transition.
this.Close();
Form1 Myform1 = new Form1()
Myform1.Show();
The problem is that when i randomly close the app, it dissapear , as i want,but it doesn't close completely.I mean it only dissappeared, but it still runs.
WHY? and HOW TO DO IT TO CLOSE ENTIRELY ?
The basic problem you are running into is that by default, your Winforms program will exit when the main form (the one that is displayed first) is closed. This is because the reference to this form is passed to the Application.Run(Form) method in the program's Main() method.
There are a variety of ways to deal with the issue, but IMHO the most straightforward is to not close the form. Instead, call the Hide() method on your main form. This will cause it simply to not be shown, but not closed. When you want to return to it, just call Show() on that form instance and it will be visible again.
Naturally, to accomplish this you will need to pass that reference to any other code that may want to use it. So you may wind up for example with code that looks like this:
this.Hide(); // Not Close()!
Form1 Myform1 = new Form1(this)
Myform1.Show();
Then somewhere in the Form1 class, where you are ready to close that and show the main form again, you would call the Show() method. That might look something like this:
partial class Form1 : Form
{
private readonly MainForm _mainForm;
public Form1(MainForm mainForm)
{
_mainForm = mainForm;
}
protected override void OnFormClosed(FormClosedEventArgs e)
{
_mainForm.Show();
}
}
Another way to handle this is to just not have the MainForm passed to the Application.Run() method in the first place. Instead, call the parameterless overload of Application.Run(). But then you will need some other mechanism for closing the program. For example, calling Application.Exit() at the appropriate time.
While this seems to me to very a fairly common question, I was unable to find another question that seemed like an exact duplicate. However, there are definitely a large number of other related questions, including the following:
C# Application.Run without Form
Close a windows form without exiting the entire application
How can I close a login form and show the main form without my application closing?
If I close one of my forms, they all close
Methods this.hide() vs this.close()
Those last two are particularly relevant, but unfortunately the top answer in each is probably the worst way to solve the problem (i.e. put each form into its own thread…one should use multiple UI threads as a last resort only, and doing so is definitely not called for here). So take any advice you read in any of the above questions with a grain of salt. There is some good information among the answers, but there is also a fair amount of bad advice as well.
I'm trying to make a new form appear when I click on a label. I'm using Windows Application Forms.
Here's the code:
private void label1_Click(object sender, EventArgs e)
{
Form parpokeru = new Form();
parpokeru.Show();
parpokeru.ShowDialog();
}
When I click on the label, a error appears (Unhandled exception has occurred in your application...). Can anyone tell me how to fix it?
Call .Show() or .ShowDialog(). Not both.
Show() will display your second form, while still allowing the user to access the first form.
ShowDialog() will display your second form as "modal". Execution of code in the first form stops while the second form is open (at least on the main thread.. for example, timers will continue to run), and the user will not be able to access your first form while the second is open.
When you call the Show method your form is shown on video like another window and the code returns immediately from the call. So your code continues and all the forms of your application are available for the user interaction. It is calledd a modeless dialog
On the contrary, ShowDialog is a blocking call. The code doesn't return from this call until something happen inside the called form that terminates the visualization of the form. As an example comes to ming a call to the methid Hide or a click on a button with its DialogResult property set to something different from DialogResult.None. At this point the code from ShowDialog returns and the normal processing continue. While the code is blocked inside the ShowDialog the application is blocked and the user cannot interact with other forms or menus or whatever is displayed on video. It is called modal dialog
Another difference is ShowDialog returns value (a DialogResult enum value) that can can be used to determine how the user closed the form (DialogResult.Cancel, DialogResult.OK), also ShowDialog does not call the Dispose method at closing time. This will allow to retrieve property from the Modal Dialog like user inputs for further processing.
I cannot imagine what happen in the internal processing of your form if, after a modeless call to Show you call immediately a ShowDialog on the same form instance. However, an exception is really the minimum to expect from this code.
I've got a WinForm Application that connects via Net.Sockets to another program.
When it gets closed per X or ALT+F4 or whatever, several routines should be processed and I need to keep the network connection until they're done.
I thought an Application.ApplicationExit Handler would do the trick, but as soon as I give the order the network connection is dead. Other important stuff can't be done.
My Form is closed instantaneously too, and I need that one a little longer.
Is Application.ApplicationExit the right tool for the job?
I put that in my Form Class that App.Runs from the Main method which is located in a different class.
You could use the Closing event of the form. It is called before the form is closed.
If you are having an open window, there are the event-handler Closing and Closed. The Closing-event is fired as soon as you click 'X', for example. Inside the method you can even decide, whether to close the window or not.
Provide an event-handler like
private void Form1_Closing(object sender, FormClosingEventArgs e){
// persist until everything is done
}
and associate it with the event
Form1.Closing += Form1_Closing;
See MSDN for documentation.
In my application I want to show a login form first and then the main form if the login has been successful. Currently I'm doing it something like this:
var A = new LoginForm();
if ( A.ShowDialog() == DialogResult.OK )
Application.Run(new MainForm());
But then I started wondering - what's the point of the Application.Run()? Why not just do (new MainForm()).ShowDialog() as well? What's the difference? And what would be the correct way to achieve what I want?
Application.Run(Form) starts a message loop on the current thread and displays the specified form. The message loop enables the form to receive Windows messages (eg, key presses, mouse clicks, paint invalidations) to allow it to appear responsive and have interaction with the user. When you call ShowDialog() on a Form instance, it actually does a similar thing and creates a modal message loop for the form on which ShowDialog has been called.
There is not much difference between the two calls. Application.Run does add some extra event handling enabling you to do some tidying up of resources when the main form is closed (see Application.ThreadExit).
The recommended way to start WinForms applications is using Application.Run, but I suspect this is more of a convention than a rule. The biggest reason to use Application.Run is if you want to open multiple non-modal forms. You can do this using:
new Form().Show();
new Form().Show();
Application.Run();
You could not achieve this using the ShowDialog() method as one of the forms would have to be modal.
As for your question of how to show a login form and then the main form if the login is successful, I think what you have is fine:
if (new LoginForm().ShowDialog() == DialogResult.OK)
{
Application.Run(new MainForm());
}
The alternative is to do the plumbing yourself and open an instance of MainForm in the closing event of the LoginForm if the login was successful.
From MSDN:
This method adds an event handler to
the mainForm parameter for the Closed
event. The event handler calls
ExitThread to clean up the
application.
http://msdn.microsoft.com/en-us/library/ms157902.aspx
From my testing, I noticed this main difference:
When Application.Run is used, the form's Close button (red X) returns DialogResult.None; however, when ShowDialog is used, the Close button produces DialogResult.Cancel.
Does this matter to you? In my code, I was testing for DialogResult.Cancel to determine the exit code of my application. That was broken when the red X was used to close the form. I now test for DialogResult.OK to indicate a successful exit.
return myForm.DialogResult == DialogResult.OK ? 0 : 1;
One key difference is that ShowDialog is usually a modal Dialog. If you wanted to create a user-friendly toolset, you would not want it to be comprised of modal dialog boxes.
Also, Application.Run() accepts more than just a form. It has a few overloads.
As for your application, I do not think it matters much. Application.Run makes sense to me because it denotes the start of your actual Application.
The documentation of the overload
public static void Run(
ApplicationContext context );
has a neat example with a different approach that involves two forms as well.
For a more concerete example of a difference:
If your main form is an MDI form, then the behavior on clicking the close button (the 'x' in the upper right, or Alt-F4) is different depending on which method you use to show the form.
With Application.Run(mainForm), the closing event of the child forms run, then the main form's closing event runs.
With mainForm.ShowDialog, the closing event of the main form runs, and the closing event of the child forms do not run.
Application.Run() is for the start of application while MainForm is part of the application and MainForm()).ShowDialog() used to display it only.
Application.Run() is the entry point for your Application. same as Main() method is for some class or ApplicationStart() for a WebApplication
Application.Run() has different overloads, one of which is without parameters. That Method starts application without an initial form.
From my testing I notice that using Application.Run buttons with DialogResult does not close the form (OnFormClosing is not hit) compare to ShowDialog in which the buttons with DialogResult hit OnFormClosing and the close the form.