[2005] DateTimePicker Valuechanged event firing twice??

This seems pretty straighforward. I have two DateTimePickers. One for a start date and the other for an end date.

I want to check when each one has changed to ensure that the dates are consistent (ie. end date is greater than start date).

This is the code I have so far.

Code:

---

      Private Sub dtp_SchTaskEnd_ValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles dtp_SchTaskEnd.ValueChanged
        Dim dtp As DateTimePicker = DirectCast(sender, DateTimePicker)
        If dtp.Value.ToShortDateString < Me.dtp_SchTaskStart.Value.ToShortDateString Then
            MessageBox.Show("End date cannot be earlier than start date", "Wrong end date", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            dtp.Value = Me.dtp_SchTaskStart.Value
        End If
    End Sub

---

However, the warning message gets shown twice if the If condition is true. Why is that?

It would probably be because you are setting the value of the datetimepicker inside the eventhandler:

VB.NET Code:

dtp.Value = Me.dtp_SchTaskStart.Value

I would do this instead:

VB.NET Code:

Private Sub DateTimePicker1_ValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DateTimePicker1.ValueChanged
        DateTimePicker2.MinDate = DateTimePicker1.Value
    End Sub
 
    Private Sub DateTimePicker2_ValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DateTimePicker2.ValueChanged
        DateTimePicker1.MaxDate = DateTimePicker2.Value
    End Sub

DateTimePicker1 can never have a date higher than the date in DateTimePicker2, and DateTimePicker2 can never have a date lower than the date in DateTimePicker1.
No need for error messages :)