Event Handler Fires Twice

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

I'm using VB.Net 2005

I have a Base Form that has a button control on it named btnEnter. The event
handler for this control is shown below:

Overridable Sub btnEnter_Click(ByVal sender As System.Object, ByVal e
As System.EventArgs) Handles btnEnter.Click
Do Something....
End Sub

Then, this form is inhertied to another form named frmOrderProcessing. But,
on this form I want to perform a different event than what the base form is
doing. So, for the btnEnter button I create the following event.

Overrides Sub btnEnter_Click(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles btnEnter.Click
MessageBox.Show("Do Something")
End Sub

Now, the click event on my second form runs correctly, except that it runs
twice. Why would this even fire twice and what must I do to make it work
correctly?

Thank You.
 
remove the 'Handles btnEnter.Click' on the derived form. You have
'subscribed' to the event twice. You only need to override the event
handler, not subscribe to the event a second time.
 
Greg said:
I'm using VB.Net 2005

I have a Base Form that has a button control on it named btnEnter.
The event handler for this control is shown below:

Overridable Sub btnEnter_Click(ByVal sender As System.Object, ByVal
e As System.EventArgs) Handles btnEnter.Click
Do Something....
End Sub

Then, this form is inhertied to another form named
frmOrderProcessing. But, on this form I want to perform a different
event than what the base form is doing. So, for the btnEnter button
I create the following event.

Overrides Sub btnEnter_Click(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles btnEnter.Click
MessageBox.Show("Do Something")
End Sub

Now, the click event on my second form runs correctly, except that
it runs twice. Why would this even fire twice and what must I do to
make it work correctly?
Click to expand...

As I've already said in your previous thread:
You don't need the "Handles" in the derived Form.


Armin
 
Greg said:
I have a Base Form that has a button control on it named btnEnter. The event
handler for this control is shown below:

Overridable Sub btnEnter_Click(ByVal sender As System.Object, ByVal e
As System.EventArgs) Handles btnEnter.Click
Do Something....
End Sub

Then, this form is inhertied to another form named frmOrderProcessing. But,
on this form I want to perform a different event than what the base form is
doing. So, for the btnEnter button I create the following event.

Overrides Sub btnEnter_Click(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles btnEnter.Click
MessageBox.Show("Do Something")
End Sub

Now, the click event on my second form runs correctly, except that it runs
twice. Why would this even fire twice and what must I do to make it work
correctly?
Click to expand...

Two "Handles" clauses; two sets of events.

Events and Inheritance (of Controls) often causes confusion like this,
which is why Our Friend in Redmond have a /different/ model for doing
with this, which goes something like this:

Class Base

' The class now has its own version of the EnterClick event
' This replaces the one coming from btnEnter itself
Public Event EnterClicked( _
sender as Object _
, e as EventArgs _
)

' This routine (and ONLY this routine) raises the event
Protected Overridable Sub OnEnterClicked( e )

' You can do things before raising the event ...

RaiseEvent EnterClicked( Me, e )

' ... and other things when the call comes back

' (You can even decide NOT to raise the event at all!)

End Sub

' a LOCAL event handler detects the actual button being clicked
Private Sub btnEnter_Click( _
sender as Object _
, e as EventArgs _
) Handles btnEnter.Click

' ... and raises the event from the enclosing class
Me.OnEnterClicked( e )

End Sub

End Class

In your derived class, you don't /want/ all the hassle of event handlers
(you want the base class to do that), but you still want to run your own
code when the button gets clicked. Easy enough; override the method
that raises the EnterClicked event.

Class Derived
Inherits Base

Protected Overrides Sub OnEnterClicked( e as EventArgs )
' Do something different.

' If you want to raise the EnterClicked event
' (to other code still waiting for it)
MyBase.OnEnterClicked( e )
End Sub

End Class

HTH,
Phill W.
 
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