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How to stop windows form from closing but hide upon clicking the X?

I'm trying to have a click event that will open another form. I don't want the user to be able to close this window because I get the following exception when the click event is executed again.
System.ObjectDisposedException: 'Cannot access a disposed object.
Object name: 'Form2'.'
I'm not sure if I'm implementing this correctly or there's a better way of doing this.
Form1
public Form2 f = new Form2();
private void Btnsearch_Click(object sender, EventArgs e)
{
f.Show();
}
Form2
private bool allowClose = false;
private void Btnclose_Click(object sender, EventArgs e)
{
allowClose = true;
this.Hide();
}
private void Form2_FormClosing(object sender, FormClosingEventArgs e)
{
if (!allowClose)
e.Cancel = true;
}

Subscribe to Form.OnClosing and set the Cancel property on the event args that are passed to the handler. This will tell the runtime to cancel the close event.
Since the event is getting canceled, you'll have to hide the form yourself (using Hide(), of course).
private void Form1_Closing(Object sender, CancelEventArgs e)
{
this.Hide();
e.Cancel = true;
}

The instance of form2 should be created within the event
private void Btnsearch_Click(object sender, EventArgs e)
{
Form2 f = new Form2();
f.Show();
}

There are a couple of ways to approach this.
It's generally more efficient, in the FormClosing event, to hide the form and cancel the event, but this can require extra logic.
Unless you have some expensive code that needs to run when the form is created, this probably doesn't matter, and it'll be easier to simply allow the form to close normally.
Either way, all you particularly need to do, is throw some safeguards into the btnSearch handler, so that it can appropriately respond to the state of form f;
public Form2 f;
public void BtnSearch_Click(object sender, EventArgs e)
{
if (f == null || f.IsDisposed || f.Disposing) f = new Form2(...);
f.Show();
}

How do I focus on a form after entering a textbox

I'm not sure if focus is the right word but I have an on key up event on my form that will open a new form and close the current form, however after i enter a textbox or other such object i can't re select the form to be able to activate the key up event
This is code a I am using currently when i click on my form, to try select my currently open form however it does not close the current form when i active the key up event, when i do it this way
private void frmLevel1_Click(object sender, EventArgs e)
{
this.BackColor = GlobalClass.BG;
frmLevel1 lvl1 = new frmLevel1();
lvl1.Select();
}

I'm not 100% sure, but you have a few different questions. I hope it helps.
// Button click event
private void button1_Click(object sender, EventArgs e)
{
// Focus on textbox
this.ActiveControl = textBox1;
}
// Form load event
private void Form1_Load(object sender, EventArgs e)
{
// Focus on textbox
this.ActiveControl = textBox1;
}
// Close the current form and open another one. Use any event what you want
private void button1_Click(object sender, EventArgs e)
{
using (Form2 frm = new Form2())
{
// Hide the current form. If you close it it will dispose of all further events
this.Hide();
// Open the new form
frm.Show();
// Close the current form
this.Close();
}
}

Closing Form C#

Recently I had to edit my program code so that the form will close after creating a PDF. In FormClosing() there's a MessageBox.Show for closing or not, depending on the DialogResult. The problem is that when I try to Close(), it shows me the MessageBox, I need to close it without showing it. Thanks.
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
if (MessageBox.Show("Exit?", "Exit", MessageBoxButtons.YesNo) == DialogResult.No)
{
e.Cancel = true;
}
}
private void btn_PdfCreate_CloseForm_Click(object sender, EventArgs e)
{
showPDf();
// close pdf but skip MessageBox
}

You can stop listening to the event like so
private void btn_PdfCreate_CloseForm_Click(object sender, EventArgs e)
{
this.FormClosing -= Form1_FormClosing
showPDf();
Close();
}

You can use the CloseReason property of the FormClosingEventArgs:
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
if (e.ClosingReason == CloseReason.UserClosing && MessageBox.Show("Exit?", "Exit", MessageBoxButtons.YesNo) == DialogResult.No)
{
e.Cancel = true;
}
}

Use e.ClosingReason to find out if the formClosing event was fired by the user's attempt to close the form, or by something else.
for further reading, go to MSDN:
http://msdn.microsoft.com/en-us/library/system.windows.forms.formclosingeventargs.closereason(v=vs.110).aspx

You anyways want to close the form after pdf creation. So call Form's Dispose method just after pdf creation like below and no need of registering for the OnFormClosing event
private void btn_PdfCreate_CloseForm_Click(object sender, EventArgs e)
{
showPDf();
this.Dispose();
}

How to close form

Ok, so a Windows Forms class, WindowSettings, and the form has a "Cancel"-button. When the user clicks the button, the dialog DialogSettingsCancel will pop-up up and ask the user if he is sure he wants to perform the action. The dialog has 2 buttons, a "Yes"-button and a "No"-button. If the user clicks the "Yes"-button, I want both DialogSettingsCancel and WindowSettings to be closed.
My button_Click event handler in DialogSettingsCancel:
private void button1_Click(object sender, EventArgs e)
{
//Code to trigger when the "Yes"-button is pressed.
WindowSettings settings = new WindowSettings();
this.Close();
settings.Close();
}
When I run my application, and go to the settings form, and click the "Cancel"-button, and then click the "Yes"-button, only DialogSettingsCancel closes without closing WindowSettings.
Why won't it work?
I've also tried changing
this.Close();
settings.Close();
to
settings.Close();
this.Close();
But still the same result.

You need the actual instance of the WindowSettings that's open, not a new one.
Currently, you are creating a new instance of WindowSettings and calling Close on that. That doesn't do anything because that new instance never has been shown.
Instead, when showing DialogSettingsCancel set the current instance of WindowSettings as the parent.
Something like this:
In WindowSettings:
private void showDialogSettings_Click(object sender, EventArgs e)
{
var dialogSettingsCancel = new DialogSettingsCancel();
dialogSettingsCancel.OwningWindowSettings = this;
dialogSettingsCancel.Show();
}
In DialogSettingsCancel:
public WindowSettings OwningWindowSettings { get; set; }
private void button1_Click(object sender, EventArgs e)
{
this.Close();
if(OwningWindowSettings != null)
OwningWindowSettings.Close();
}
This approach takes into account, that a DialogSettingsCancel could potentially be opened without a WindowsSettings as parent.
If the two are always connected, you should instead use a constructor parameter:
In WindowSettings:
private void showDialogSettings_Click(object sender, EventArgs e)
{
var dialogSettingsCancel = new DialogSettingsCancel(this);
dialogSettingsCancel.Show();
}
In DialogSettingsCancel:
WindowSettings _owningWindowSettings;
public DialogSettingsCancel(WindowSettings owningWindowSettings)
{
if(owningWindowSettings == null)
throw new ArgumentNullException("owningWindowSettings");
_owningWindowSettings = owningWindowSettings;
}
private void button1_Click(object sender, EventArgs e)
{
this.Close();
_owningWindowSettings.Close();
}

You can also close the application:
Application.Exit();
It will end the processes.

new WindowSettings();
You just closed a brand new instance of the form that wasn't visible in the first place.
You need to close the original instance of the form by accepting it as a constructor parameter and storing it in a field.

Why not use the DialogResult method to close the form?
if(DialogSettingsCancel.ShowDialog() == DialogResult.Yes)
{
//this will close the form but will keep application open if your
//application type is "console" in the properties of the project
this.Close();
}
For this to work however you will need to do it inside your "WindowSettings" form while you call the DialogSettingsCancel form. Much the same way you would call the OpenFileDialog, or any other Dialog form.

Your closing your instance of the settings window right after you create it. You need to display the settings window first then wait for a dialog result. If it comes back as canceled then close the window. For Example:
private void button1_Click(object sender, EventArgs e)
{
Settings newSettingsWindow = new Settings();
if (newSettingsWindow.ShowDialog() == DialogResult.Cancel)
{
newSettingsWindow.Close();
}
}

send the WindowSettings as the parameter of the constructor of the DialogSettingsCancel and then on the button1_Click when yes is pressed call the close method of both of them.
public class DialogSettingsCancel
{
WindowSettings parent;
public DialogSettingsCancel(WindowSettings settings)
{
this.parent = settings;
}
private void button1_Click(object sender, EventArgs e)
{
//Code to trigger when the "Yes"-button is pressed.
this.parent.Close();
this.Close();
}
}

for example, if you want to close a windows form when an action is performed there are two methods to do it
1.To close it directly
Form1 f=new Form1();
f.close(); //u can use below comment also
//this.close();
2.We can also hide form without closing it
private void button1_Click(object sender, EventArgs e)
{
Form1 f1 = new Form1();
Form2 f2 = new Form2();
int flag = 0;
string u, p;
u = textBox1.Text;
p = textBox2.Text;
if(u=="username" && p=="pasword")
{
flag = 1;
}
else
{
MessageBox.Show("enter correct details");
}
if(flag==1)
{
f2.Show();
this.Hide();
}
}

There are different methods to open or close winform.
Form.Close() is one method in closing a winform.
When 'Form.Close()' execute , all resources created in that form are destroyed.
Resources means control and all its child controls (labels , buttons) , forms etc.
Some other methods to close winform
Form.Hide()
Application.Exit()
Some methods to Open/Start a form
Form.Show()
Form.ShowDialog()
Form.TopMost()
All of them act differently , Explore them !

Interaction between forms in WinForms application, c#

guys!
I've got 2 forms in application - working form (frmMain) and form of settings (frmSettings).
There are two buttons on frmSettings - Save and Cancel. In frmMain I use the following approach to show the frmSettings:
private void btnSettings_Click(object sender, EventArgs e)
{
frmSettings = new SettingsForm();
frmSettings.ShowDialog();
// ...
}
The problem is I don't know, how to detect, which button was pressed on the frmMain - Save or Cancel. The further logic of the program depends on this fact. I need something like this:
private void btnSettings_Click(object sender, EventArgs e)
{
frmSettings = new SettingsForm();
frmSettings.ShowDialog();
if(/* frmSettings.SaveButton.WasClicked == true */)
{
InitializeServices();
}
// ...
}
Please, give me an advice, how to implement such kind of interaction between forms. Better without using global variables for saving buttons state.
Thanks beforehand.

ShowDialog returns a DialogResult object that allow you to know that. You have to:
On Save Button's click event, set this.DialogResult to DialogResult.OK
On Cancel Button's click event, set this.DialogResult to DialogResult.Cancel
private void btnSettings_Click(object sender, EventArgs e)
{
frmSettings = new SettingsForm();
if(frmSettings.ShowDialog() == DialogResult.OK)
{
InitializeServices();
}
//.......
}
Edited to manage the DialogResult as #tsiorn's answer: setting form's DialgoResult insted of setting that property on each button.

You chould use DialogResult to handle this. On your form settings window, you can set the result as so:
protected void btnSave_Click(object sender, EventArgs e) {
DialogResult = System.Windows.Forms.DialogResult.OK
this.close;
}
protected void btnCancel_Click(object sender, EventArgs e) {
DialogResult = System.Windows.Forms.DialogResult.Cancel;
this.close;
}
Then ...
private void btnSettings_Click(object sender, EventArgs e)
{
frmSettings = new SettingsForm();
frmSettings.ShowDialog();
if(frmSettings.DialogResult == DialogResult.OK)
{
// save
InitializeServices();
}
// ...
}

Start with an enumeration of the possible values:
public enum ExitMethod
{
Other, //this should be first, as a default value
Save,
Cancel,
Error
}
Then make a property on SettingsForm of that type:
public ExitMethod ExitMethod { get; private set; }
In SettingsForm's save/exit methods set that property to the appropriate enum value, and in the main form you can read that property value.

in the frmSettings window you handle the Click events on the buttons. Then set the dialog result:
void frmSettings_Save_Click(object sender, EventArgs e)
{
this.DialogResult = DialogResult.OK;
}
void frmSettings_Cancel_Click(object sender, EventArgs e)
{
this.DialogResult = DialogResult.Cancel;
}
in the main form you do something like this to capture and evaluate the result:
DialogResult answer = frmSettings.ShowDialog();
if (answer == DialogResult.OK)
{
...
}
Additional information and usage can be found here:
http://msdn.microsoft.com/en-us/library/system.windows.forms.form.dialogresult.aspx