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How to detect if a window is closed C#, Windows Form App?

So, I'm making a payroll management system as a hobby project to help my resume and general knowledge of c#. So, I'm making a UI and I can open a new window just fine with this code:
private void button1_Click(object sender, EventArgs e)
{
CreateAdminAcct createAcct = new CreateAdminAcct();
createAcct.StartPosition = FormStartPosition.CenterScreen;
createAcct.Show();
this.Hide();
}
however, I don't know the event to check when the little red "x" button is clicked, because when that button is clicked, I want to go back to the main screen because I hide the main screen when that button is clicked, and when i click the red "x" on the screen that just opened, it closes, but the application continues to run in the background.
If there is some better way to manage multiple menus, I'm open to suggestions, however, this is what I've found easiest.
Thanks in advance

I second Robert Harvey's suggestion; this gives the user the reassurance tha tht emain window is still open/ nothing got lost, but it's unreachably "behind" the CreateAdminAcct form while the CreateAdminAcct form is open
private void button1_Click(object sender, EventArgs e)
{
CreateAdminAcct createAcct = new CreateAdminAcct();
createAcct.StartPosition = FormStartPosition.CenterScreen;
createAcct.ShowDialog();
//do any code here that needs to access createAcct before it's lost
MessageBox.Show(createAcct.NewAdmin.Name);
}
If you really do want to hide your main form, pass the main form itself to createAcct, and make it createAcct's job to re-open the main form when it is closing
private void button1_Click(object sender, EventArgs e)
{
CreateAdminAcct createAcct = new CreateAdminAcct(this); //note passing this form to constructor
createAcct.StartPosition = FormStartPosition.CenterScreen;
createAcct.Show();
}
class CreateAcctForm : Form{
private Form _showWhenClosing;
CreateAcctForm(Form revertTo){
InitializeComponent();
_showWhenClosing = revertTo;
}
}
void Form_Closing(object sender, ...){ //event
_showWhenClosing.Show();
}
Side note: please rename your controls after you drop them ona form. code that's stuffed with label57, textbox25 is effectively obfuscated and really wearisome to follow

Windows form application sequential ShowDialog()s

well I have a funny problem with closing dialog forms.
here is the problem:
I run application and open second form (through menu strip) as showdialog(); and then from second form open third form. When I open third form by button 1 and then close it everything is alright, but when I open the third form by button 2 and then close it, third form will be closed and then it closes the second form also. !!! In second form when I show a messageBox and close it also the second form will be closed.
here is my codes:
open second form from first form codes:
private void settingsToolMenu_Click(object sender, EventArgs e)
{
settingsForm s1 = new settingsForm(this);
s1.ShowDialog();
}
open third form from second by button 1 form codes:
private void addReportButton_Click(object sender, EventArgs e)
{
addReport a1 = new addReport(this);
a1.ShowDialog();
}
open third form from second by button 2 form codes:
private void editReportButton_Click(object sender, EventArgs e)
{
addReport a2 = new addReport(this);
a2.ShowDialog();
}
as you see there is no differences between button 1 and button 2
here is a video from application running.

Not sure what's happening out there, but there should be .Show() method, which runs a window in a different way including closing strategy. Try it out.

Try This
Instead of
addReport a2 = new addReport(this);
a2.ShowDialog();
Use
addReport a2 = new addReport();
a2.ShowDialog(this);
Then on click of Exit / Close button of dialog window
private void BtnExit_Click(object sender, EventArgs e)
{
this.Dispose();
}
Hope this will solve your issue.

I used this code and it worked. I have 3 forms, the first form is opened when running the app, the second form is opened with a button (can be menustrip, doesn't matter), then the third is opened like that too, after closing the third form the second form remains open.
FormN fm = new FormN();
fm.ShowDialog();
Use that piece of code in every method that is called from clicking on a button and it should work fine. Just change the "FormN" for whatever your forms are named. Also, if you need to pass any form's attributes into the next form you can do this:
Code at first form:
public string mytext; //Variable I want to use later, in Form2.
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
mytext = tb1.Text;
Form2 fm = new Form2(this);
fm.ShowDialog();
}
Notice how I save "tb1"'s (TextBox1) value in a variable before calling "fm.ShowDialog();", so I can use the TextBox1 value later inside the Form2.
Code at second form, having main form's variables (such as "mytext" value).
Form1 mfm;
public Form2(Form1 mainfm)
{
InitializeComponent();
mfm = mainfm;
}
public void button2_Click(object sender, EventArgs e)
{
//In this method I use the variable "mytext" wich is a Form1 attribute.
//You can see how I declare it in the first form's code (see above).
textBox1.Text = mfm.mytext;
}
With this you have created an object of your main form ("Form1 mfm;") with all the variables it contained before calling the second form, which can be used for the third form too.

in second form formClosing() event i wrote these codes:
private void settingsForm_FormClosing(object sender, FormClosingEventArgs e)
{
if(e.CloseReason != CloseReason.UserClosing)
{
e.Cancel = true;
}
}
and nothing can close the second form except user!

How to open recently closed or hide form

I've researched thoroughly but still i cant find the best solution for this..
I have a 3 buttons, BACK - HOME - FORWARD ..
This is just like the buttons on the upper left of browser .. and im trying to do this on a form..
what i have is this ..
the back button code is
private void button1_Click(object sender, EventArgs e)
{
this.Hide();
}
// simply hiding the form .. so that the previous form will be shown..
the home button code is this..
private void button2_Click(object sender, EventArgs e)
{
for (int i = Application.OpenForms.Count - 1; i >= 0; i--)
{
if (Application.OpenForms[i].Name != "HomePage")
Application.OpenForms[i].Close();
}
}
// this will show the HomePage form and close other forms whos name is not "HomePage"
the Problem is when i press the Back Button , im hiding it .. how can a button will re open a previously closed or hided form ?
I hope you can Help me! Thanks!
private void button3_Click(object sender, EventArgs e)
{
???????
}

You would need to store a reference to the form that you wish to open again.
There are a couple of options to do this, but if you simply wanted to allow the user to go "Forward" once, you could just store a reference to the form like so:
internal class MyHistory {
internal static Form LastForm;
}
// ........
private void button1_Click(object sender, EventArgs e)
{
MyHistory.LastForm = this;
this.Hide();
}
// ........
private void button3_Click(object sender, EventArgs e)
{
MyHistory.LastForm.Show();
}
Of course, you could maintain a full stack of history items and traverse back/forwards through them if you wanted to be more comprehensive than this.
Note that, if you .Close() your form, you won't be able to reopen it as the reference will be disposed of once it is closed. This method would only work if you were to .Hide() it, which keeps the form instance valid, just hides the form from the user's view.

you could use a form list which holds all initialized forms. that way you can hide, show, add and remove forms dynamically.
List<Form> lstForms = new List<Form>();
then when you add a form:
Form newForm = new Form();
lstForms.Add(newForm);
Hiding a Form:
lstForms(x).Hide(); //x = index of Form you want to hide
Showing a Form
lstForms(x).Show(); //x = index of Form you want to hide
Removing a Form (when closing it for example)
lstForms.RemoveAt(x);
that way you can dynamically work with forms and it is much easier to keep an overview if you have many forms...

Cannot access a disposed object?

I have a countdown Timer form - on the first form the user will enter the countdown time - warning times, end message, etc. There are also two Radio buttons (Max/Min) and depending on which is selected they will open a new Max or Min form where the time will actually start to countdown. It is working fine and counting down as I expect. However, if I exit the Max or Min form and try to run again with new times I get the error. The code is below - note the comment out ShowDialog(this); was something I tried - it let me close and open the new forms ok but it did not actually start the countdown. UpdateLabels is the function that does the updating of Labels.
bool Max = rbMax.Checked;
if (Max == true)
{
//_Max.ShowDialog(this);
_Max.Show();
}
else
//_Min.ShowDialog(this);
_Min.Show();
UpdateLabels();
}
I also tried the following which I read online as a possible solution but it also did not work...
private void Max_FormClosing(object sender, FormClosingEventArgs e)
{
this.Hide();
this.Parent = null;
}
Can anyone help me out - I can post the UpdateLabels function if needed. I am pretty new to UI C# development so any help would be great. Thanks.

The problem is, that a closed form can not be used anymore (be reopened). Thats why the code you posted tries to stop closing and only hides your window. But for doing this, the Cancel-property must be set to true:
private void Max_FormClosing(object sender, FormClosingEventArgs e) {
this.Hide();
this.Parent = null;
e.Cancel=true;
}
To show the form after closing it this way, show it with the Show() method.
However this is probably only a workaround and you could solve the problem with another design.
Maybe it would be wise, to create a new instance of your form, every time you need it, instead of trying to reopen it every time. This also has the advantage that the form only requesires resources if it is really needed.

What you can do is add a following check before calling .Show method:
if(_Max == null || _Max.IsDisposed)
_Max = new MaxForm();
_Max.Show();
and similarly for _Min form

Whenever a form is closed, all its resources are freed. This means that you can't access the object any more, since it no longer exists - it's been freed and deleted from memory. To prevent that, you can cancel the closing of the form, and hide it instead (which will appear transparent to the user).
this.Hide();
e.Cancel=true;
An updated version of your code is as follows:
private void Max_FormClosing(object sender, FormClosingEventArgs e)
{
e.Cancel = true;
this.Hide();
this.Parent = null;
}

The solution is simple that instantiate the object of the called form in the button click event e.g.
private void buttonSetting_Click( object sender, EventArgs e )
{
***_setting = new SettingWindow();*** //When I need to show the settings window
_setting.Show();
}

create new instatnce if object is not available
if(frmRGB==nullptr || frmRGB.IsDisposed==true )
{
frmRGB= new Form();
}

Create Object inside button click event
like this
private void btn_supplier_order_Click(object sender, EventArgs e)
{
form_supplier_order so = new form_supplier_order();
so.Show();
}

Winform appears twice

I am working on a personal project in winforms just to gain some experience in it since I've never had the chance to work with it before. So, I'm quite the n00b when it comes to Winforms. This is the error I'm encountering:
In form BudgetTracker, I have a button called 'AddCat'. Below is the form's constructor and the button's click eventHandler:
public form_BudgetTracker()
{
InitializeComponent();
setEvents();
}
public void setEvents()
{
this.btn_AddCat.Click += new System.EventHandler(this.btn_AddCat_Click);
}
private void btn_AddCat_Click(object sender, EventArgs e)
{
form_NewCat NewCatForm = new form_NewCat();
var NewCatFormResult = NewCatForm.ShowDialog();
NewCatForm.Show();
}
In the NewCat form that comes up, I have a Cancel button. Code:
public form_NewCat()
{
InitializeComponent();
SetEvents();
}
private void SetEvents()
{
this.btn_Add.Click += new System.EventHandler(this.btn_Add_Click);
this.btn_Cancel.Click += new System.EventHandler(this.btn_Cancel_Click);
}
private void btn_Cancel_Click(object sender, EventArgs e)
{
this.Close();
}
The problem I'm facing is, when I click Add, the new form comes up. At this point, if I click Cancel, the form disappears but instantly a new instance of the form appears. I then click cancel again, and the form disappears.
What part of my code is making the form appear twice. I checked the contructors etc, but couldn't figure it out. Any help or pointers would be appreciated.
PS - As I mentioned, I'm new to winforms programming, so any cues or pointers would be appreciated as well.

private void btn_AddCat_Click(object sender, EventArgs e)
{
form_NewCat NewCatForm = new form_NewCat();
var NewCatFormResult = NewCatForm.ShowDialog(); // <-- opens the first time
NewCatForm.Show(); // <-- opens the second time
}

Judging from your code, you're simply showing the form twice!!!
form_NewCat NewCatForm = new form_NewCat();
var NewCatFormResult = NewCatForm.ShowDialog();
NewCatForm.Show();
The second line shows the form and blocks the method until DialogResult is set, then the third line shows the form without blocking the method.
Simply remove the third line!

Try stepping through the code using the F8 key instead of running it, or hitting F5. It will show you line by line what it's about to execute.

delete NewCatForm.Show();