Raising events in Derived classes

[kejpa]

Hi,

I'm having a object hierarchy where I want to raise events in the derived classes but it's not working the way I want it to.

 

Public Interface iSensor

Event NewData(ByVal SensorValues() As Integer, ByVal TimeStamp As Single, ByVal Sensor As iSensor)
.	Sub ReadSensor()

.
End Interface

Public MustInherit Class c485Sensor
Implements iSensor
Public Event NewData(ByVal SensorValues() As Integer, ByVal 
TimeStamp As Single, ByVal Sensor As iSensor) Implements iSensor.NewData
Public MustOverride Sub ReadSensor() Implements iSensor.ReadSensor

.
End Class

Public Class c485Specialized
Inherits c485Sensor
Public Shadows Event NewData(ByVal SensorValues() As Integer, ByVal TimeStamp As Single, ByVal Sensor As iSensor)

.
Public Overrides Sub ReadSensor()
	RaiseEvent(imodValues, DateAndTime.Timer,Me
End Sub

If I shadows the event in the 485Specialized class it won't be raised unless I explicitly calls it from the Applications Form :

AddHandler ctype(oSensor(0),c485Specialized).NewData, AddressOf oSensor_SensorData

 

What I want is to raise the event in the derived class without having to ctype it.

Is there something wrong with my hierarchy?

Shouldn't the "Shadows" keyword shadow the base class procedures and let the derived classes handle the calls?

 

I'm confused. Again :confused:

Thank God it's Friday

/Kejpa

[Nerseus]

To "call an event in a derived" class, you need only call a function in your base class and mark the base method as overridable (VB) or virtual (C#).

 

For example:

Base class A: Create a method "CallMe" with no code (unless you want seme default behavior, in which case put in some code). Make sure it's marked overridable or virtual.

 

From the method that you want to raise the event from, just call this method (CallMe).

 

Inherited Class B (inherts from A): Override the method CallMe to do whatever you want. When class A needs to "call the event" it's really just calling the method in class B.

 

You would only need events if you want an outside class to get the event. In that case, do the above AND have class A's CallMe raise an event that an outside class could hook into. (If you do this, then class B's CallMe method would first call base.CallMe() to get that default behavior of raising the event.)

 

-nerseus