Add Confirmation Dialog Box When Closing a VB.NET form

To prevent your user from accidentally closing a form, you can add a confirm dialog that will ask first if the user indeed want to close the active form or cancel it instead. With this form behavior you can prevent losing unsaved work. In VB.NET, you can trap closing of form on FormClosing attribute. FormClosing event occurs whenever the user closes the form and before the form has been closed. Any code written on this block is executed first before the program close the active window.



To ask for confirmation, copy and paste the following code inside the FormClosing event:

        If MessageBox.Show("This will close this form. Continue?", "Confirm Closing", MessageBoxButtons.YesNo) = Windows.Forms.DialogResult.No Then
            e.Cancel = True
        End If

The MessageBox will provide user the option to continue closing by clicking the "Yes" button or cancel it by hitting the "No" button. If user presses the "No" button, VB will assign true to the Cancel property of the "e" argument variable that will abort the closing of the form.

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