Override standard close X button in a Windows Form

Question

How do I go about changing what happens when a user clicks the close  red X  button in a Windows Forms application  in C

User · Answer

Override the OnFormClosing method   CAUTION   You need to check the CloseReason and only alter the behaviour if it is UserClosing   You should not put anything in here that would stall the Windows shutdown routine   Application Shutdown Changes in Windows Vista  This is from the Windows 7 logo program requirements

User · Answer

One thing these answers lack  and which newbies are probably looking for  is that while it s nice to have an event   private void Form1 FormClosing object sender  FormClosingEventArgs e           do something     It s not going to do anything at all unless you register the event  Put this in the class constructor   this FormClosing    Form1 FormClosing

User · Answer

One situation where it is quite useful to be able to handle the x-button click event is when you are using a Form that is an MDI container  The reason is that the closeing and closed events are raised first with children and lastly with the parent  So in one scenario a user clicks the x-button to close the application and the MDI parent asks for a confirmation to proceed  In case he decides to not close the application but carry on whatever he is doing the children will already have processed the closing event potentially lost information work whatever  One solution is to intercept the WM CLOSE message from the Windows message loop in your main application form  i e  which closed  terminates the application  like so       protected override void WndProc ref Message m                if  m Msg    0x0010     WM CLOSE                          If we don t want to close this window              if  ShowConfirmation  Are you sure       DialogResult Yes  return                     base WndProc ref m

User · Answer

as Jon B said  but you ll also want to check for the ApplicationExitCall and TaskManagerClosing CloseReason   protected override void OnFormClosing FormClosingEventArgs e        if    e CloseReason    CloseReason WindowsShutDown            e CloseReason    CloseReason ApplicationExitCall           e CloseReason    CloseReason TaskManagerClosing            return             e Cancel   true        assuming you want the close-button to only hide the form         and are overriding the form s OnFormClosing method      this Hide

User · Answer

The accepted answer works quite well  An alternative method that I have used is to create a FormClosing method for the main Form  This is very similar to the override  My example is for an application that minimizes to the system tray when clicking the close button on the Form   private void Form1 FormClosing object sender  FormClosingEventArgs e                if  e CloseReason    CloseReason ApplicationExitCall                        return                    else                       e Cancel   true              WindowState   FormWindowState Minimized                                This will allow ALT F4 or anything in the Application calling Application Exit    to act as normal while clicking the  X  will minimize the Application

User · Answer

Either override the OnFormClosing or register for the event FormClosing     This is an example of overriding the OnFormClosing function in the derived form   protected override void OnFormClosing FormClosingEventArgs e       e Cancel   true      This is an example of the handler of the event to stop the form from closing which can be in any class   private void FormClosing object sender FormClosingEventArgs e         e Cancel   true      To get more advanced  check the CloseReason property on the FormClosingEventArgs to ensure the appropriate action is performed  You might want to only do the alternative action if the user tries to close the form

User · Answer

protected override bool ProcessCmdKey ref Message msg  Keys dataKey                if  dataKey    Keys Escape                        this Close                  this Visible   false                Plus clear values from form  if Visible false                    return base ProcessCmdKey ref msg  dataKey

User · Answer

You can override OnFormClosing to do this  Just be careful you don t do anything too unexpected  as clicking the  X  to close is a well understood behavior   protected override void OnFormClosing FormClosingEventArgs e        base OnFormClosing e        if  e CloseReason    CloseReason WindowsShutDown  return          Confirm user wants to close     switch  MessageBox Show this   Are you sure you want to close     Closing   MessageBoxButtons YesNo             case DialogResult No          e Cancel   true          break      default          break

User · Answer

This is a pretty commonly asked question   One good answer is here   VB NET overload default functionality when user clicks the X  Close Program     If you don t feel comfortable putting your code in the Form Closing event  the only other option I am aware of is a  hack  that I ve used once or twice   It should not be necessary to resort to this hack  but here it is     Don t use the normal close button   Instead  create your form so that it has no ControlBox   You can do this by setting ControlBox   false on the form  in which case  you will still have the normal bar across the top of the form  or you can set the form s FormBorderStyle to  None  If you go this second route  there will be no bar across the top  or any other visible border  so you ll have to simulate those either by drawing on the form  or by artistic use of Panel controls   Then you can add a standard button and make it look like a close button  and put your clean-up code in there   At the end of the button event  just call this Close    C   or Me Close    VB

User · Answer

Override OnFormClosing

[c#] Override standard close (X) button in a Windows Form

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