Develop Reference

C# - Override the Standard Windows Close Button to Pop-up my Custom Form

Yes, noob question. My apologies.
When users click on the red x button on the window, I want to pop up a message asking if they really would want to quit. I found a similar question on this site: Override standard close (X) button in a Windows Form.
The thing is, I want to customize the font and the MessageBoxIcon for the MessageBox, and sadly it can't be done (or will take a lot of effort to be done). So, I've decided to make my own form.
protected override void OnFormClosing(FormClosingEventArgs e)
{
if (txtID.Text != "" || txtPassword.Text != "")
{
base.OnFormClosing(e);
if (e.CloseReason == CloseReason.WindowsShutDown) return;
// Confirm user wants to close
new formConfirmExit().ShowDialog();
}
}
I added this code under the main form. However, when I run my code and I click on the standard close button, my pop up (the custom form I did) doesn't do what it's job. Suppose I click the "No" button, it terminates my entire program. With the "Yes" button, the pop-up shows up again, and then everything kinda stops (on Visual Studio) and ta-da! an exception.
BTW, these are the Yes and No button methods (from my Custom Form's class):
private void btnYes_Click(object sender, EventArgs e)
{
Application.Exit(); // terminate program (exception is in here)
}
private void btnNo_Click(object sender, EventArgs e)
{
this.Close(); // close this pop up window and go back to main window
}
Changing Application.Exit() to Environment.Exit(0) did the job for the Yes button, but my No button, well, terminates the program, still.
Edit: When I click on the Yes button, the pop-up/my custom form shows again (just one time). It'll stay on that state (I can click on the Yes button repeatedly yet nothing happens). The InvalidOperationException is thrown when I click the Yes button first (note the first sentence of this paragraph) then the No button.
Thank you.

Add this in your No_Click:
private void btnNo_Click(object sender, EventArgs e)
{
DialogResult = DialogResult.No;
}
Then, change your forms closing event to the following:
protected override void OnFormClosing(FormClosingEventArgs e)
{
if (txtID.Text != "" || txtPassword.Text != "")
{
base.OnFormClosing(e);
if (e.CloseReason == CloseReason.WindowsShutDown
|| e.CloseReason == CloseReason.ApplicationExitCall)
return;
// Confirm user wants to close
using(var closeForm = new formConfirmExit())
{
var result = closeForm.ShowDialog();
if (result == DialogResult.No)
e.Cancel = true;
}
}
}
First, it checks if the form isn't closing through Application.Exit(), this may be triggered from your other form, so it will not reshow the custom MessageBox.
Second, you create a using statement around your custom form. This way you can preserve the values. You then set the dialogresult to no, if the user doesn't want to cancel. If this is the case, set e.Cancel = true to stop from exiting.

C# Handle a dialog's button click in another form

I have a form. In that I got to show a dialog (on some circumstances) with Text and a Cancel button. I want to catch the event of that button in my form Or know if that cancel button was clicked.
How can this be done ? I believe this should be possible but can't make out how ?
From my mainForm I have BackgroundWorker. When the backgroundWorker is started I open a childForm (with a Label and a button) and when the background task is over, I close the childForm. What I want more is : when the button of childForm is clicked the ongoing task of backgroundWorker should be cancelled.
SOLUTION
In my childForm I have set CancelButton property as cancelBtn for the form. The othe code is :
private bool cancel;
public bool Cancel
{
get { return cancel; }
set { cancel = value; }
}
// Set the flag as true to indicate that Cancel button was actually pressed
private void cancelBtn_Click(object sender, EventArgs e)
{
Cancel = true;
}
In mainForm :
childDlg = new ChildDialog();
// wHILE cALLING
backgroundWorker1.RunWorkerAsync();
msg = "Connecting...";
childDlg .set(msg, "");
if (!childDlg .IsAccessible)
{
// This is caught even when the dialog is closed
if (childDlg .ShowDialog() == DialogResult.Cancel) {
if (childDlg.Cancel == true) { // Was really cancelBtn pressed
// NOW ONLY do my stuff
}
}
}
I had tried using #DeveloperX technique i.e. EventHandler in parent class, but the parent class method was nver being called. Tried a lot but couldn't success. Then tried of #RobinJ's technique and it worked. I just had to add flag to identify was really cancel button pressed or jjst windw was closed normally.
Thanks to all of you for tryig to help me out. I really appreciate your help.
Thanks

Set DialogResult property to either DialogResult.Ok or DialogResult.Cancel
Then in the parent form:
Form form = new Form();
DialogResult results = form.DialogResult;
if(results == DialogResult.Ok)
{
... make magic
}
else
{
...
}

Put this in the form that should catch the event:
frmDialog.ShowDialog();
And this in the btnCancel_Click event of the dialog:
return DialogResult.Cancel();
Sorry if I'm confusing VB and C# here, but it's pretty much the same.

Simply you can create an event for the form that shows the dialog
and handle this event in parent form
in case the user clicks on ok fire event with specefic parameter and for cancel another parameter (such dialogresult.cancel)
an pseudo implementation can be like this
public class FormChild : System.Windows.Forms.Form
{
public event EventHandler DialogCanceled;
public event EventHandler DialogConfirmed;
public void ShowDialog()
{
using (var dialogForm = new FormDialog())
{
if (dialogForm.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
if (DialogConfirmed != null)
DialogConfirmed(this,new EventArgs());
}
else
{
if (DialogCanceled != null)
DialogCanceled(this,new EventArgs());
}
}
}
}
public class ParentForm : System.Windows.Forms.Form
{
public void callChild()
{
using (var f = new FormChild())
{
f.DialogCanceled += new EventHandler(f_DialogCanceled);
f.DialogConfirmed += new EventHandler(f_DialogConfirmed);
f.ShowDialog();
}
}
void f_DialogConfirmed(object sender, EventArgs e)
{
throw new NotImplementedException();
}
void f_DialogCanceled(object sender, EventArgs e)
{
throw new NotImplementedException();
}
}

You should be using the ShowDialog method on the form you need to show as a dialog and then use the DialogResult property to communicate to the parent form the result of the dialog operation.
This way you handle the button click on the form that owns the button but set the DialogResult to DialogResult.Cancel to specify that the user pressed the cancel button.

A dialog is usually a blocking event, where eventhandling by the parent form would make no sense at all.
If it isn't a modal dialog, you can always create one or several public events in the popup form, that are triggered when the buttons are clicked. These events can then be caught by the parent form.
Don't expose your buttons to the parent form, it would be terrible oo-programming.

Use the following:
Form form = new Form();
switch (form.ShowDialog())
{
case DialogResult.Ok:
{
....
Break;
}
case DialogResult.Cancel:
{
....
Break;
}
}
Set the Form.AcceptButton and Form.CancelButton properties to the appropriate buttons.
Refer to the following:
Form.ShowDialog Method
DialogResult Enumeration
Form.AcceptButton Property
Form.CancelButton Property

c# cancel application from closing if hidden form has unsaved changes

after searching google and stackoverflow I'm unable to find an answer that helped me in my situation. I've got an application with a start menu(form). when the user presses the X(close) of a (any) form I reload the start menu. Now when that(menu) form gets closed I want to check and notify the user wheter any now hidden forms are in editing mode (with or without unsaved changes) if user presses cancel I want to show that form and stop the application from closing. Now my problem is how do i stop the application from stopping in the code of the other forms. I have an override of the dispose method of the subforms that calls this.close so the ok/cancel messagebox shows but after the MB the start menu closes anyway stopping the program. Should I look for a different method of handling these things or is there a method or eventhandler to modify so this /\ can work?
EDIT:
ok here's parts of the code in order of being called. Where does i go wrong?
private void Menu_FormClosing(object sender, FormClosingEventArgs e)
{
Global.Forms.Remove(this);
if (!Global.Clean_Forms())
{
e.Cancel = true;
Global.Forms.Add(this);
}
}
public static void Clean_Forms()
{
foreach (Form f in Forms)
{
if (f is Menu)
{
//do nothing
}
else
{
if (!f.IsDisposed)
{
f.Close();
}
}
}
if (Forms.Count != 0)
{
isClean = false;
/* String a = "";
foreach (Form f in Forms)
{
a += f.ToString() + ": ";
}
MessageBox.Show(a);*/
}
else
{
isClean = true;
}
}
Yet this doesnt work, application just closes down.
the closing event handler of random form
private void persoon_form_FormClosing(object sender, FormClosingEventArgs e)
{
if (editing)
{
DialogResult dr;
dr = MessageBox.Show("uw wijzigingen gaan verloren. Doorgaan?", "sluiten", MessageBoxButtons.OKCancel);
if (dr == DialogResult.Cancel)
{
e.Cancel = true;
}
else if (dr == DialogResult.OK)
{
Global.size = this.Size;
Global.position = this.Location;
Global.Forms.Remove(this);
Form f = Global.menu();
f.Show();
this.Dispose();
}
}//somethingelse}
EDIT: #cody gray changed onclose and clean_form still no effect, (shouldn't the messagebox in the Closing event of the subform be shown anyway? cause it doesnt)

You should not be doing this in the Dispose method. Instead, try handling the FormClosing event.
This event occurs before the form is closed, so you can check whatever state you need to, and cancel the close if necessary by setting e.Cancel to True.
For example:
protected override void OnFormClosing(FormClosingEventArgs e)
{
base.OnFormClosing(e);
// Check to see if the user is allowed to close this form
if (!allowClose)
{
// Prevent this form from being closed
MessageBox.Show("This form cannot be closed yet!");
e.Cancel = true;
}
}

I think i figured it out! I changed two things. 1 I made sure that I didn't call this.dispose anywhere as that will result in disposing (not closing) any child forms hence no onclosing event is called. 2. the foreach loop when checking if main menu can close generated collection was modified errors. so with this I made sure it closes in the right order thnx Cody Gray for pointing me in the right direction:
Stack<Form> stack = new Stack<Form>();
foreach (Form f in Forms)
{
if (f is Menu)
{
//do nothing
}
else
{
if (!f.IsDisposed)
{
stack.Push(f);
}
}
}
for (int i = 0; i < stack.Count; i++)
{
Form temp = stack.Pop();
temp.Close();
}

Retain the dialog to be open after ShowDialog result

I'm opening a modal dialog asking the user to fill certain fields.
if(dlgUserDetail.ShowDialog() == DialogResult.OK)
{
}
On click of OK, the control comes to the parent form where I'm validating the user input.
If the validation fails, I wanted to keep the dialog to be open with the old values. Since it is modal dialog, the form gets closed.
It seems to be a common problem as I see many discussion on net, but nowhere I was able to find a solution.
Please let me know how to solve this problem. Thanks.
Regards
ArunDhaJ

If it is your dialog you could add a CancelEventArgs event called Validate or InputOk (similar to FileOk in OpenFileDialog) and have your main form check the input in a method. Before calling DialogResult = DialogResult.OK in your dialog, you add a ´onValidate` call to check if the input is valid.
{
// dialog
{
if (onValidate()) {
DialogResult = DialogResult.OK;
}
}
private bool onValidate() {
CancelEventHandler handler = Validate;
if (handler == null) {
return true;
}
CancelEventArgs args = new CancelEventArgs();
handler(this, args);
return args.Cancel;
}
}
{
// form
{
dlgUserDetail.Validate += valid;
if(dlgUserDetail.ShowDialog() == DialogResult.OK) { }
}
private void valid(object sender, CancelEventArgs e) {
// check input and set
e.Cancel = true;
// if not valid
}
}

One solution is to put validate logic into dlgUserDetail form and invoke it on OnClosing event. If the validation failed then prevent the form from closing.

Preventing a dialog from closing in the button's click event handler

I have a dialog that I show with <class>.ShowDialog(). It has an OK button and a Cancel button; the OK button also has an event handler.
I want to do some input validation in the event handler and, if it fails, notify the user with a message box and prevent the dialog from closing. I don't know how to do the last part (preventing the close).

You can cancel closing by setting the Form's DialogResult to DialogResult.None.
An example where button1 is the AcceptButton:
private void button1_Click(object sender, EventArgs e) {
if (!validate())
this.DialogResult = DialogResult.None;
}
When the user clicks button1 and the validate method returns false, the form will not be closed.

Given that you've specified you want a pop error dialog, one way of doing this is to move your validation into a OnClosing event handler. In this example the form close is a aborted if the user answers yes to the question in the dialog.
private void Form1_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
// Determine if text has changed in the textbox by comparing to original text.
if (textBox1.Text != strMyOriginalText)
{
// Display a MsgBox asking the user to save changes or abort.
if(MessageBox.Show("Do you want to save changes to your text?", "My Application",
MessageBoxButtons.YesNo) == DialogResult.Yes)
{
// Cancel the Closing event from closing the form.
e.Cancel = true;
// Call method to save file...
}
}
}
By setting e.Cancel = true you will prevent the form from closing.
However, it would be a better design/user experience to display the validation errors inline (via highlighting the offending fields in some way, displaying tooltips, etc.) and prevent the user from selecting the OK button in the first place.

Don't use the FormClosing event for this, you'll want to allow the user to dismiss the dialog with either Cancel or clicking the X. Simply implement the OK button's Click event handler and don't close until you are happy:
private void btnOk_Click(object sender, EventArgs e) {
if (ValidateControls())
this.DialogResult = DialogResult.OK;
}
Where "ValidateControls" is your validation logic. Return false if there's something wrong.

You can catch FormClosing an there force the form to remain opened.
use the Cancel property of the event argument object for that.
e.Cancel = true;
and it should stop your form from closing.

This doesn't directly answer your question (other already have), but from a usability point of view, I would prefer the offending button be disabled while the input is not valid.

Use this code:
private void btnOk_Click(object sender, EventArgs e) {
if (ValidateControls())
this.DialogResult = DialogResult.OK;
}
The problem of it is that the user has to clic two times the buttons for closing the forms;

Just add one line in the event function
private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e)
{
this->DialogResult = System::Windows::Forms::DialogResult::None;
}

I wish I had time to find a better example, but you would be much better off using the existing windows forms validation techniques to do this.
http://msdn.microsoft.com/en-us/library/ms229603.aspx

void SaveInfo()
{
blnCanCloseForm = false;
Vosol[] vs = getAdd2DBVosol();
if (DGError.RowCount > 0)
return;
Thread myThread = new Thread(() =>
{
this.Invoke((MethodInvoker)delegate {
picLoad.Visible = true;
lblProcces.Text = "Saving ...";
});
int intError = setAdd2DBVsosol(vs);
Action action = (() =>
{
if (intError > 0)
{
objVosolError = objVosolError.Where(c => c != null).ToArray();
DGError.DataSource = objVosolError;// dtErrorDup.DefaultView;
DGError.Refresh();
DGError.Show();
lblMSG.Text = "Check Errors...";
}
else
{
MessageBox.Show("Saved All Records...");
blnCanCloseForm = true;
this.DialogResult = DialogResult.OK;
this.Close();
}
});
this.Invoke((MethodInvoker)delegate {
picLoad.Visible = false;
lblProcces.Text = "";
});
this.BeginInvoke(action);
});
myThread.Start();
}
void frmExcellImportInfo_FormClosing(object s, FormClosingEventArgs e)
{
if (!blnCanCloseForm)
e.Cancel = true;
}

You can probably check the form before the users hits the OK button. If that's not an option, then open a message box saying something is wrong and re-open the form with the previous state.