In a recent multi-tab VB.NET Web application, the values from a 3 controls on a tab (tab A) were used as filters for a dropdownlist on a subsequent tab (tab B). If the controls on tab A were changed, the dropdownlist on tab B would be reloaded based on the changed value(s).
In the event that all 3 controls changed, I didn’t want the dropdownlist reloaded 3 times, so I decide to use delegates as one solution.
' Fields Private Delegate Sub DentalBlueDelegate() Private _dbd As DentalBlueDelegate Private _mcd As [Delegate] ' Methods Private Sub ReloadDentalBlue() ' If the delegate does not have anything assigned the dental ' blue delegate is added. A multicast delegate is used to ' prevent multiple calls to the same method from the different ' TextChanged event handlers that need to trigger a reload of ' the DentalBlue dropdownlist. If _mcd Is Nothing Then _mcd = MulticastDelegate.Combine(_mcd, _dbd) _mcd.DynamicInvoke(Nothing) End If End Sub Private Sub txtParticipating_TextChanged(ByVal sender As Object, _ ByVal e As System.EventArgs) Handles txtParticipating.TextChanged ReloadDentalBlue() End Sub
