Tracking change of control variable.

[tc]

I'm trying to put together a small control. It's not, but for arguments
sake, let's say it's a progress bar.

The user will make a change to a setting, lets call it 'value'.

I want to trap the change of the public variable in the controls code so I
can act on that change.

How would I do that?

[Patrice]

Use a property instead of a public variable :
http://msdn2.microsoft.com/en-us/lib...57(VS.80).aspx

You may want to read the whole spec at least once so that you know what is
available :
http://msdn2.microsoft.com/en-us/lib...37(vs.80).aspx

---
Patrice

"tc" <tu**@idcodeware.co.uka écrit dans le message de news:
O0*************@TK2MSFTNGP06.phx.gbl...

I'm trying to put together a small control. It's not, but for arguments
sake, let's say it's a progress bar.

The user will make a change to a setting, lets call it 'value'.

I want to trap the change of the public variable in the controls code so I
can act on that change.

How would I do that?

[rowe_newsgroups]

On Aug 29, 8:06 am, "Patrice" <http://www.chez.com/scribe/wrote:

Use a property instead of a public variable :http://msdn2.microsoft.com/en-us/lib...57(VS.80).aspx

You may want to read the whole spec at least once so that you know what is
available :http://msdn2.microsoft.com/en-us/lib...37(vs.80).aspx

---
Patrice

"tc" <[e-mail] écrit dans le message de news:
[e-mail]...

I'm trying to put together a small control. It's not, but for arguments
sake, let's say it's a progress bar.

The user will make a change to a setting, lets call it 'value'.

I want to trap the change of the public variable in the controls code so I
can act on that change.

How would I do that?

To build on Patrice's statements:

I would change the public variable (which should almost always be
avoided imo) into a public property. In the Set accessor I would
inspect the value to see if it is different than the current value and
if so I would fire off the necessary events.

Something like (untested):

//////////////////////
Public Class TheClass

Public Property MyProperty() As String
Get
Return _MyProperty
End Get
Set(ByVal value As String)
Dim isDifferent As Boolean = (value <_MyProperty)
If isDifferent Then OnMyPropertyChanging(EventArgs.Empty)
_MyProperty = value
If isDifferent Then OnMyPropertyChanged(EventArgs.Empty)
End Set
End Property
Private _MyProperty As String = ""

Public Event MyPropertyChanging As EventHandler
Public Event MyPropertyChanged As EventHandler

Protected Overridable Sub OnMyPropertyChanging(ByVal e As
EventArgs)
RaiseEvent MyPropertyChanging(Me, e)
End Sub

Protected Overridable Sub OnMyPropertyChanged(ByVal e As
EventArgs)
RaiseEvent MyPropertyChanged(Me, e)
End Sub

End Class
////////////////////

That way you have events that can notify any listeners both before and
after the change to the property occurs.

Thanks,

Seth Rowe

[tc]

Thanks for your input peeps.

"rowe_newsgroups" <ro********@yahoo.comwrote in message
news:11**********************@57g2000hsv.googlegro ups.com...
On Aug 29, 8:06 am, "Patrice" <http://www.chez.com/scribe/wrote:

Use a property instead of a public variable
:http://msdn2.microsoft.com/en-us/lib...57(VS.80).aspx

You may want to read the whole spec at least once so that you know what is
available :http://msdn2.microsoft.com/en-us/lib...37(vs.80).aspx

---
Patrice

"tc" <[e-mail] écrit dans le message de news:
[e-mail]...

I'm trying to put together a small control. It's not, but for arguments
sake, let's say it's a progress bar.

The user will make a change to a setting, lets call it 'value'.

I want to trap the change of the public variable in the controls code so
I
can act on that change.

How would I do that?

To build on Patrice's statements:

I would change the public variable (which should almost always be
avoided imo) into a public property. In the Set accessor I would
inspect the value to see if it is different than the current value and
if so I would fire off the necessary events.

Something like (untested):

//////////////////////
Public Class TheClass

Public Property MyProperty() As String
Get
Return _MyProperty
End Get
Set(ByVal value As String)
Dim isDifferent As Boolean = (value <_MyProperty)
If isDifferent Then OnMyPropertyChanging(EventArgs.Empty)
_MyProperty = value
If isDifferent Then OnMyPropertyChanged(EventArgs.Empty)
End Set
End Property
Private _MyProperty As String = ""

Public Event MyPropertyChanging As EventHandler
Public Event MyPropertyChanged As EventHandler

Protected Overridable Sub OnMyPropertyChanging(ByVal e As
EventArgs)
RaiseEvent MyPropertyChanging(Me, e)
End Sub

Protected Overridable Sub OnMyPropertyChanged(ByVal e As
EventArgs)
RaiseEvent MyPropertyChanged(Me, e)
End Sub

End Class
////////////////////

That way you have events that can notify any listeners both before and
after the change to the property occurs.

Thanks,

Seth Rowe