How to prevent the Calendar from hiding, on clicking the button "Today" or "None" in DateTimePickerAdv?

bool flag = false;
//Occurs mouse button click
void NoneButton_MouseDown(object sender, MouseEventArgs e)
{
    flag = true;
}
//Occurs mouse button click
void NoneButton_MouseUp(object sender, MouseEventArgs e)
{
    flag = false;
}
//To prevent the popup window hiding
void PopupWindow_BeforeCloseUp(object sender, CancelEventArgs e)
{
    if (flag)
    e.Cancel = true;
}
//Another way
//To display the calendar when click on the Today or Non button
void TodayButton_Click(object sender, EventArgs e)
{
    dateTimePickerAdv1.DisplayCalendar();
}
void Calendar_NoneButtonClick(object sender, EventArgs e)
{
    dateTimePickerAdv1.DisplayCalendar();
}

Dim flag As Boolean = false
'Occurs mouse button click
Private Sub NoneButton_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs)
    flag = true
End Sub
'Occurs mouse button click
Private Sub NoneButton_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs)
    flag = false
End Sub
'To prevent the popup window hiding
Private Sub PopupWindow_BeforeCloseUp(ByVal sender As Object, ByVal e As CancelEventArgs)
    If flag Then 
        e.Cancel = true
    End If
End Sub

'Another way to display the calendar when click on the Today or Non button
Private Sub TodayButton_Click(ByVal sender As Object, ByVal e As EventArgs)
    dateTimePickerAdv1.DisplayCalendar()
End Sub
Private Sub Calendar_NoneButtonClick(ByVal sender As Object, ByVal e As EventArgs)
    dateTimePickerAdv1.DisplayCalendar()
End Sub