C#

static void Main() 
{
  Application.EnableVisualStyles();
  Application.Run(new Form1());
}

AddButton_click<br />
{<br />
this.tabControl1.Selecting += tabControl1_Selecting;<br />
}<br />
<br />
    private void tabControl1_Selecting(object sender, TabControlCancelEventArgs e)<br />
    {<br />
      MessageBox.Show("Please Cancel or Save your changes before going any further.", "Action required", MessageBoxButtons.OK, MessageBoxIcon.Question);<br />
      this.tabControl1.Selecting -= tabControl1_Selecting;// <-- stops the message from popping up twice.<br />
      tabControl1.SelectedIndex = 2; <-- I'll code this to refer to the appropriate calling tab page index.<br />
      this.tabControl1.Selecting += tabControl1_Selecting; // in case the user didn't get the message the first time :)<br />
    }

private void tabControl1_Selecting(object sender, TabControlCancelEventArgs e)
{
  MessageBox.Show("Please Cancel or Save your changes before going any further.", "Action required", MessageBoxButtons.OK, MessageBoxIcon.Question);
  e.Cancel = true;
}