标题：[求助]主窗口BeforeClose事件不执行？

Dim sd As WinForm.DateTimePicker
Dim ed As WinForm.DateTimePicker
sd = e.Form.Controls("StartDate")
ed = e.Form.Controls("EndDate")
If sd.Value Is Nothing OrElse ed.Value Is Nothing Then
    MessageBox.Show("请输入起始日期和终止日期！","提示", MessageBoxButtons.OK ,MessageBoxIcon.Information)
    e.Cancel = True
End If

主窗口可能没有这个事件吧