VB.net : How can I prompt a user if they are about to close their program with unsaved data?

Question

I working working with Visual Basic 2010 Express. I have a DataGridView that is linked up with a local SQL database I've created. I have it currently where the user can click a button to save their data to the db, but am unsure how to prompt them to save or discard changes if they are closing the program without saving.

Thanks!

Answer 1

Keep a global boolean (Dim _bDocumentChanged as boolean) and when any DataGridView events are fired set your boolean to True and then on the Form_Closing() check that boolean and throw a message box.

Answer 2

I think you should also provide a cancel so the user can cancel the close without having to save the data or lose the changes they already made. Something like this:

    Private Sub frmMain_FormClosing(ByVal sender As Object, _
        ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing

    Dim Answer As DialogResult = MessageBox.Show("Save Data before close?", _
        "Data Check", MessageBoxButtons.YesNoCancel)

    Select Case Answer
        Case Windows.Forms.DialogResult.Yes
            SaveRecords()
        Case Windows.Forms.DialogResult.No
            Exit Sub
        Case Windows.Forms.DialogResult.Cancel
            e.Cancel = True
        Case Else
            Exit Sub
    End Select

End Sub