I have program that opens subwindows inside of it (mdi.parent). I have made component that is in one window under it, however, i want that that window never actually disposed after its created because i want to keep only one instance of it.
This can be made with code:
// This prevents this window disposing from window close button, we want always show one and only
// one instance of this window.
FormClosing += (o, e) =>
{
Hide();
e.Cancel = true;
};
However, after this there is problem, closing program requires pressing close button press twice. First press closes subwindow and second terminates program. How this can be get around?
I am working with Winforms.
As Habib said, you can call Application.Exit, but:
The Form.Closed and Form.Closing events are not raised when the
Application.Exit method is called to exit your application
If this is important to you, you can do something like this (MDI parent code):
private Boolean terminating;
protected override void OnClosing(CancelEventArgs e)
{
if (!terminating)
{
terminating = true;
Close();
}
base.OnClosing(e);
}
Call Application.Exit() in the form close event.
Application.Exit - MSDN
Informs all message pumps that they must terminate, and then closes
all application windows after the messages have been processed.
The code inside of your FormClosing event handler method is a bit too terse. It does its job of preventing the user from closing the form, but as you've also noticed, it prevents you from closing the form programmatically as well.
This is easily solved by testing the value of the CloseReason property of the FormClosingEventArgs that are passed in each time the event is raised.
These will tell you the reason why the form is attempting to close. If the value is CloseReason.UserClosing, then you want to set e.Cancel to true and hide the form. If the value is something else, then you want to allow the form to continue closing.
// This prevents this window disposing when its close button is clicked by the
// user; we want always show one and only one instance of this window.
// But we still want to be able to close the form programmatically.
FormClosing += (o, e) =>
{
if (e.CloseReason == CloseReason.UserClosing)
{
Hide();
e.Cancel = true;
}
};
Use This
Form[] ch = this.MdiChildren;
foreach (Form chfrm in ch)
chfrm.Close();
You can use Application.Exit if there is no processing happening when the application is closed. Otherwise, you can check Application.OpenForms collection in MDI parent's closing event and close all the other forms that are open.
Related
I have several modeless Forms with grids to show data in a MDI Windows Forms app (Form1 in example code). Each of these Forms has a button that opens another Form as modal using ShowDialog (Form2 in example code), which allows editing the data shown in Form1. These modal forms have a Cancel button that closes the form without saving changes by setting DialogResult to Cancel.
I want to implement a timer that closes all forms after a certain time has elapsed from user login into the app. The problem arises if the timer triggers while a modal Form is open.
public partial class Form1 :
{ //Constructor ommited for brevity
private void btnEditData_Click(object sender, EventArgs e)
{
var form2 = new Form2();
timer1.Tick += (_, __) =>
{
form2.DialogResult = DialogResult.Cancel;
this.Close(); // this executes before form2.ShowDialog returns
};
timer1.Interval = 5_000;
timer1.Enabled = true;
form2.ShowDialog();
reloadData(); // here Form1 is already disposed because Close
// has been called on it. An exception is thrown as a consequence
}
private void reloadData()
{
if (this.IsDisposed)
// simulate using a disposed form
throw new ObjectDisposedException(this.Name);
}
}
My intention would be to somehow schedule the call Form1.Close() after form2.ShowDialog() has returned and the btnEditData_Click method has finished, so that there would be no danger of using a disposed form.
EDIT
After seeing your code, I'd suggest to introduce a third option in your Tick event handler that would be used to decide if you have to close the form. For example, Abort.
timer1.Tick += (_, __) =>
{
form2.DialogResult = DialogResult.Abort;
};
if (form2.ShowDialog() == DialogResult.Abort) Close();
else reloadData();
First thought: keep it simple and keep it clean. You don't have to keep track of your open forms, in an MDI application there is MdiChildren property of the parent form that will give you all the forms.
Then, to handle the closing part, you can use existing functionalities in .Net.
A difficult approach is using P/Invoke. You load Windows DLLs and use their functions to enumerate through all your forms and close which one you want. You can also simulate a click on Cancel button. You have to start with EnumWindows function (to identify the forms) and EnumChildWindows for form's children. I like this option because you have full control of your forms and controls, but can give you headaches if not familiar with the concept.
You can have a look at FormClosing event and subscribe to it. This event fires before the form is closed and you can make the clean up using it.
Using OOP - inheritance and override. Either you create a base form with custom close function that does the cleaning (and then inherit all your forms through it), or override form's close functions to achieve your goal.
We created a new form that we're showing via ShowDialog and added a "Cancel" button to it. Here's how we're opening the form from its parent:
// _modalForm is a class-level instance of our ModalForm class
var result = _modalForm.ShowDialog(this);
MessageBox.Show(result.ToString());
Here's the cancel button's Click event handler in ModalForm.
private void btnCancel_Click(object sender, EventArgs e)
{
Close();
}
In our FormClosing event, we have this code (based on this answer).
private void ModalForm_FormClosing(object sender, FormClosingEventArgs e)
{
e.Cancel = true;
Hide();
_parentForm.RefreshData();
}
Surprisingly, when we click the "Cancel" button (or use the "X" button at the top of the form), the FormClosing event is raised twice. Both times the CloseReason is UserClosing.
I double checked to make sure InitializeComponent isn't call twice and that we only subscribe to the event once. btnCancel is not set at the CancelButton property for the form. It also doesn't have DialogResult set in the designer. When I check the return value of ShowDialog though, it is set to DialogResult.Cancel.
Changing btnCancel_Click to just be DialogResult = DialogResult.Cancel instead of Close() and doing nothing except _parentForm.Refresh() in the FormClosing event fixes the issue of the event getting raised twice.
Does anyone know why in this particular scenario the FormClosing event gets raised twice?
That's because hiding a modal form will cause it to close with DialogResult.Cancel as dialog result. So if you call this.Hide() in FormClosing event, the event will be raised again.
Imagine if it didn't close the form, your application had been blocked by a hidden modal form!
Note: The answer describes about the reason of raising the event twice. But as described here and others mentioned, For modal forms (which you showed using ShowDialog), the Dispose method will not be called and the form exists after closing and you can use its properties to get some data or you can show it again. So you don't need to call hide method.
For more information take a look at: Do I need to Dispose a Form after the Form got Closed?
The workaround you mention is unnecessary, because modal dialogs are not disposed when closed. They are designed to keep their data after being closed (since it is required by the caller of the modal dialog), and to be reused as needed.
Just let it close properly. It causes no harm to a modal dialog :)
Note that this also means that unlike normal forms, you must dispose of modal dialogs manually if they are not persistent. In your scenario, this most likely means you'd want to dispose of the dialog when the parent form is disposed (this happens automatically if you added the dialog as a component, but needs to be done manually if you create it yourself).
I want to prevent closing of a form in some cases. I know the usage of OnFormClosing,
but when the form is hidden (Visible==false), the OnFormClosing method is not called.
Is there a way to intercept form closing in this case?
Edit (some more details):
The form is a child in a MdiParent, should stay invisible in the background and wait for calls from another thread (by Invoke).
The MdiParent closes all child windows when the user "disconnects", in this case the above form should stay open, but invisible and still waiting for calls.
When the MidParent itself is closed, all forms should close.
Edit2 (no solution?):
It seems that there is no solution to this. My workaround now is to exclude my not-to-be-closed form in the MdiParent-code, that closes all other forms.
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
// This will cancel the event
e.Cancel = true;
}
Regardless of the reason, this will effectively stop a form from closing.
I have 2 forms ...when i start the application..and use the close "X" from the title bar the entire application closes...now when i select an option from the 1st form in my case it is a button "ADD" as its a phonebook application..it goes to the 2nd form as i have used 1stform.hide() and 2ndform.show()...now when i do "X" from the title bar it doesnt shutdown completely as the 1stform is not closed....how to program it in such a way tht any stage the entire application should close
Your first form is set as the startup form. That means whenever it gets closed, your entire application is closed. And conversely, your application does not close until it gets closed. So when you hide the startup form and show the second form, the user closing the second form does not trigger your application closing because they have only closed a secondary, non-modal dialog.
I recommend changing your design so that the startup form is also the main form of your application. No sense trying to work around built-in functionality that can actually be useful. You want the application to quit when the main form is closed, no matter what other child forms are opened.
But the quick-and-dirty solution in your case is to make a call to Application.Exit. That will close all of the currently open forms and quit your application immediately. As I said just above, I don't so much recommend this approach because having to call Application.Exit from every form's FormClosed event handler is a sign that something has gone seriously wrong in your design.
If the single startup form paradigm doesn't work out for you, you should look into taking matters into your own hands and customizing the Main method in your Program.cs source file. See the answers given to this related question for some ideas on how that might work for you.
What you can do is to use the Form's FormClosing event, and add the following code:
Application.Exit();
This will stop the entire application, and close all windows. However, if a background thread is running, the process itself will survive. In this case you can use:
Environment.Exit();
Add a Application.Exit on every forms's Closing event
like this:
Create an closing event handler first
private void Form_ClosingEventhandler()(object sender, CancelEventArgs e)
{
//Perform any processing if required like saving user settings or cleaning resources
Application.Exit();
}
then bind this event to any form you create.
//Where you create new form and show it.
Form1 frm= new Form1();
//set other properties
frm.Closing += new EventHandler(Form_ClosingEventhandler);
Form2 frm2= new Form2();
//set other properties
frm2.Closing += new EventHandler(Form_ClosingEventhandler);
Surely you don't want to shut down the entire application after the user adds a phone number? You just need to make sure that your main window becomes visible again. Write that like this:
private void AddButton_Click(object sender, EventArgs e) {
var frm = new AddPhoneNumber();
frm.StartPosition = FormStartPosition.Manual;
frm.Location = this.Location;
frm.Size = this.Size; // optional
frm.FormClosing += delegate { this.Show(); };
frm.Show();
this.Hide();
}
I have a MDI main form. On it I host a form, and I want it to show a message box before it closes (asking the user whether to save changes).
So far so good, however I have discovered that closing the MDI main form does not raise a MDI child FormClosing event. I figured I will just call MdiChild.Close() in the MDI main's FormClosing event (which does get raised). This seams to work, however it does causes a problem...
In the messagebox that I show, I offer the user to save changes, not to save changes and cancel closing. Normally this works fine, however I can't seem to find a way to cancel MDI main's FormClosing event. Is there a elegant way of doing this?
EDIT: I solved this by throwing an exception (when user decides to cancel the closing procedure) which is caught in MDI main's FormClosing event. In this way I know when I have to cancel the MDI main's FormClosing event and this seams to work fine ... However I just can't believe that this "hax" is the only way of doing this. Surely there is a better way?
I figure that you cancel the close on the childform when the user votes to cancel the close?
In that case I'd go with this Main form close
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
if (e.CloseReason == CloseReason.UserClosing)
{
foreach (Form frm in this.MdiChildren)
{
frm.Close();
}
}
e.Cancel = (this.MdiChildren.Length > 0);
}
I'd suggest that instead of calling Close on the childforms you could create a method like ReadyToClose in the child forms and then the main form loops through and calls that for each of the child forms and it'll ask the question to the user and do the saving if needed and finally it'll return true if ok to continue.
And if all of the child forms "vote" for a close, then you close it all down, otherwise you close nothing.
When closing the MDI main form, all child Close events are called first so, when calling frm.Close() on the foreach loop, Close events for the child are called again (I don't know why if they should be already closed).
ho1 suggestion worked pretty well for me. Here is my modified foreach loop (ClosableMDIChildForm is an interface which contains the IsOkToClose() method):
foreach (ClosableMDIChildForm cmdif in this.MdiChildren)
{
if (!cmdif.IsOkToClose())
{
e.Cancel = true;
((Form)mdifc).Focus();
break;
}
}
Obviously, this.MdiChildren forms must implement ClosableMDIChildForm interface. The logic to decide if it's OK to close the window goes in the implementation of IsOkToClose().