Hi Guys,
I'm trying to work out how events work in VB.NET Basically I want to
create a base class that has an Event. I would like all derived
classes to inherit this event. I sorta worked out how to do that but
the real problem I have is that If I have a base class with an event
and derived class 1 and 2 inherit this event. Say derived class 1
creates a new derived class 2 how does this new class 2 get the same
event as derived class 1 without adding handlers each time. The
program below works only because I add the addhandler each time, is
this the correct way of doing it ?
Ideally I would like to have a system where I have an event in the
base class that raises an event on the UI thread and any derived
classes just call the base class event handler. It seems the code
below won't work if I don't have the addhandler statements at each
step
Level 2 code has this statement:
AddHandler l2.UpdateHandle r, AddressOf MyBase.Update
without it I would never get the messagebox("lev el 2") to show even
though the event does fire.
Can someone please help?
MAIN FORM
=========
Public Sub StartTesting()
Dim l1 As New Level1
Dim l2 As New Level2
AddHandler l1.UpdateHandle r, AddressOf RealUpdate <==== (* ADD
HANDLER)
Dim t1 As New System.Threadin g.Thread(Addres sOf
l1.SpawnThreads )
t1.Start()
End Sub
Public Sub RealUpdate(ByVa l text As String)
MsgBox(text)
End Sub
BASE CLASS
==========
Public MustInherit Class ThreadedClass
Protected Sub RaiseDataChange d(ByVal text As String)
'RaiseEvent UpdateHandler(t ext)
'Update(text)
RaiseEvent UpdateHandler(t ext)
End Sub
' Event Handler (Update)
Public Event UpdateHandler(B yVal text As String)
Private __updateText As String = "Base"
Public Property updateText() As String
Get
Return __updateText
End Get
Set(ByVal Value As String)
__updateText = Value
End Set
End Property
' Update Method raising event
Public Sub Update(ByVal text As String)
RaiseEvent UpdateHandler(t ext)
End Sub
End Class
' Level 1 (inherited)
=============== ======
Public Class Level1
Inherits ThreadedClass
Public Sub SpawnThreads()
Dim l2 As New Level2
l2.RunningProce ss()
AddHandler l2.UpdateHandle r, AddressOf MyBase.Update
Dim t1 As New System.Threadin g.Thread(Addres sOf
l2.RunningProce ss)
t1.Start()
RaiseDataChange d("Level2")
End Sub
End Class
' Level 1 (inherited)
=============== ======
Public Class Level2
Inherits ThreadedClass
Public Sub RunningProcess( )
RaiseDataChange d("Level2")
End Sub
End Class
Regards Dotnetshadow 2 3972
Here is an example i knocked up.
Public Class Base
Public Event BaseEvent(ByVal o As Object, ByVal e As EventArgs)
Private m_Text As String = ""
Public Property text() As String
Get
Return m_text
End Get
Set(ByVal Value As String)
If m_Text <> Value Then RaiseEvent BaseEvent(Me,
EventArgs.Empty )
m_Text = Value
End Set
End Property
End Class
Public Class SubClass
Inherits Base
End Class
// IN THE FORM CLASS
Private WithEvents s As New SubClass
Private Sub Button1_Click(B yVal sender As System.Object, ByVal e As
System.EventArg s) Handles Button1.Click
s.text = "Hello"
End Sub
Private Sub HandleMyEvent(B yVal o As Object, ByVal e As EventArgs)
Handles s.BaseEvent
MessageBox.Show ("Event Raised")
End Sub
--
OHM ( Terry Burns )
. . . One-Handed-Man . . .
Time flies when you don't know what you're doing
"DotNetShad ow" <ro*********@ne tscape.net> wrote in message
news:98******** *************** ***@posting.goo gle.com... Hi Guys,
I'm trying to work out how events work in VB.NET Basically I want to create a base class that has an Event. I would like all derived classes to inherit this event. I sorta worked out how to do that but the real problem I have is that If I have a base class with an event and derived class 1 and 2 inherit this event. Say derived class 1 creates a new derived class 2 how does this new class 2 get the same event as derived class 1 without adding handlers each time. The program below works only because I add the addhandler each time, is this the correct way of doing it ?
Ideally I would like to have a system where I have an event in the base class that raises an event on the UI thread and any derived classes just call the base class event handler. It seems the code below won't work if I don't have the addhandler statements at each step
Level 2 code has this statement: AddHandler l2.UpdateHandle r, AddressOf MyBase.Update without it I would never get the messagebox("lev el 2") to show even though the event does fire.
Can someone please help?
MAIN FORM ========= Public Sub StartTesting() Dim l1 As New Level1 Dim l2 As New Level2 AddHandler l1.UpdateHandle r, AddressOf RealUpdate <==== (* ADD HANDLER)
Dim t1 As New System.Threadin g.Thread(Addres sOf l1.SpawnThreads ) t1.Start() End Sub
Public Sub RealUpdate(ByVa l text As String) MsgBox(text) End Sub
BASE CLASS ========== Public MustInherit Class ThreadedClass
Protected Sub RaiseDataChange d(ByVal text As String)
'RaiseEvent UpdateHandler(t ext) 'Update(text) RaiseEvent UpdateHandler(t ext)
End Sub
' Event Handler (Update) Public Event UpdateHandler(B yVal text As String) Private __updateText As String = "Base"
Public Property updateText() As String Get Return __updateText End Get Set(ByVal Value As String) __updateText = Value End Set End Property
' Update Method raising event Public Sub Update(ByVal text As String) RaiseEvent UpdateHandler(t ext) End Sub
End Class
' Level 1 (inherited) =============== ====== Public Class Level1 Inherits ThreadedClass
Public Sub SpawnThreads()
Dim l2 As New Level2 l2.RunningProce ss() AddHandler l2.UpdateHandle r, AddressOf MyBase.Update Dim t1 As New System.Threadin g.Thread(Addres sOf l2.RunningProce ss) t1.Start()
RaiseDataChange d("Level2")
End Sub
End Class
' Level 1 (inherited) =============== ====== Public Class Level2 Inherits ThreadedClass
Public Sub RunningProcess( )
RaiseDataChange d("Level2") End Sub
End Class
Regards Dotnetshadow
* ro*********@net scape.net (DotNetShadow) scripsit: I'm trying to work out how events work in VB.NET Basically I want to create a base class that has an Event. I would like all derived classes to inherit this event. I sorta worked out how to do that but the real problem I have is that If I have a base class with an event and derived class 1 and 2 inherit this event. Say derived class 1 creates a new derived class 2 how does this new class 2 get the same event as derived class 1 without adding handlers each time. The program below works only because I add the addhandler each time, is this the correct way of doing it ?
Ideally I would like to have a system where I have an event in the base class that raises an event on the UI thread and any derived classes just call the base class event handler. It seems the code below won't work if I don't have the addhandler statements at each step
Level 2 code has this statement: AddHandler l2.UpdateHandle r, AddressOf MyBase.Update without it I would never get the messagebox("lev el 2") to show even though the event does fire.
Can someone please help?
MAIN FORM ========= Public Sub StartTesting() Dim l1 As New Level1 Dim l2 As New Level2 AddHandler l1.UpdateHandle r, AddressOf RealUpdate <==== (* ADD HANDLER)
'l1' and 'l2' are different objects, so adding handlers to one of them
won't add them to the other object.
--
Herfried K. Wagner [MVP]
<URL:http://dotnet.mvps.org/> This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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create a base class that has an Event. I would like all derived
classes to inherit this event. I sorta worked out how to do that but
the real problem I have is that If I have a base class with an event
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