Hi
I have a created a custom web control called ImageBrowser, extract is
below:
<Code>
#Region "Properties "
Public Property Images() As ImageCollection
Get
If ViewState("Imag es") Is Nothing Then
ViewState("Imag es") = New ImageCollection
End if
Return CType(ViewState ("Images"), GalleryImageCol lection)
End Get
Set(ByVal Value As ImageCollection )
ViewState("Imag es") = Value
End Set
End Property
Public Property CurrentImage() As Integer
Get
Return CInt(ViewState( "CurrentImage") )
End Get
Set(ByVal Value As Integer)
ViewState("Curr entImage") = Value
End Set
End Property
#End Region
#Region "Initilizat ion"
Private Sub Page_PreRender( ByVal sender As Object, ByVal e As
System.EventArg s) Handles MyBase.PreRende r
If Not IsPostBack Then GetData() 'populates Images
collection from database
AddImages()
End Sub
Private Sub AddImages
Dim Image as WebControls.Ima ge
Dim ImageCounter as Integer
For Each Image in Images
Dim ImageButton as New WebControls.Ima geButton
ImageButton.Ima geUrl = Image.ImageUrl
ImageButton.ID = "Image" & ImageCounter.To String
Me.Controls.Add (ImageButton)
AddHandler ImageButton.Cli ck, AddressOf Image_Click
ImageCounter += 1
Next
End Sub
#End Region
#Region "Implementation "
Private Sub Image_Click(ByV al sender As Object, ByVal e As
System.Web.UI.I mageClickEventA rgs)
Dim ImageName As String = CType(sender, ImageButton).ID
CurrentImage = CInt(ImageName. Substring(5))
End Sub
#End Region
</Code>
Within the AddImages function each image in the Images collection is
added to the control as an ImageButton, I have to do this in the
prerender because i need to know what the CurrentImage property is
from the ViewState and this in the first place i have found it to be
populated.
The only problem is that the event for the ImageButton.Cli ck is not
firing, i believe this is because i have added it to late in the page
life cycle. This appears to be a but of a nasty circle. Does anyone
know where i am going wrong?
Thanks
Blu 2 1357
Eww..
Yeah I think you know your problem already, you need to call AddImages from page_load and not PreRender. By PreRender it is one step too late to process Handlers, as that step just passed.
Here is a good article on the ASP.NET page lifecycle, it may help understanding when viewstate gets populated, I don't see why you couldn't do it in page_load, perhaps you could share your problems when you try that next. http://www.15seconds.com/Issue/020102.htm
Happy Coding!
--Michael
"BluDog" <ne**@nospam.bl udog.net> wrote in message news:gs******** *************** *********@4ax.c om... Hi I have a created a custom web control called ImageBrowser, extract is below: <Code> #Region "Properties " Public Property Images() As ImageCollection Get If ViewState("Imag es") Is Nothing Then ViewState("Imag es") = New ImageCollection End if Return CType(ViewState ("Images"), GalleryImageCol lection) End Get Set(ByVal Value As ImageCollection ) ViewState("Imag es") = Value End Set End Property Public Property CurrentImage() As Integer Get Return CInt(ViewState( "CurrentImage") ) End Get Set(ByVal Value As Integer) ViewState("Curr entImage") = Value End Set End Property #End Region #Region "Initilizat ion" Private Sub Page_PreRender( ByVal sender As Object, ByVal e As System.EventArg s) Handles MyBase.PreRende r If Not IsPostBack Then GetData() 'populates Images collection from database AddImages() End Sub Private Sub AddImages Dim Image as WebControls.Ima ge Dim ImageCounter as Integer For Each Image in Images Dim ImageButton as New WebControls.Ima geButton ImageButton.Ima geUrl = Image.ImageUrl ImageButton.ID = "Image" & ImageCounter.To String Me.Controls.Add (ImageButton) AddHandler ImageButton.Cli ck, AddressOf Image_Click ImageCounter += 1 Next End Sub #End Region #Region "Implementation " Private Sub Image_Click(ByV al sender As Object, ByVal e As System.Web.UI.I mageClickEventA rgs) Dim ImageName As String = CType(sender, ImageButton).ID CurrentImage = CInt(ImageName. Substring(5)) End Sub #End Region </Code> Within the AddImages function each image in the Images collection is added to the control as an ImageButton, I have to do this in the prerender because i need to know what the CurrentImage property is from the ViewState and this in the first place i have found it to be populated. The only problem is that the event for the ImageButton.Cli ck is not firing, i believe this is because i have added it to late in the page life cycle. This appears to be a but of a nasty circle. Does anyone know where i am going wrong? Thanks Blu
On Fri, 28 May 2004 12:30:34 -0400, "Raterus" <ra*****@spam.o rg>
wrote: Eww..
Yeah I think you know your problem already, you need to call AddImages from page_load and not PreRender. By PreRender it is one step too late to process Handlers, as that step just passed.
Here is a good article on the ASP.NET page lifecycle, it may help understanding when viewstate gets populated, I don't see why you couldn't do it in page_load, perhaps you could share your problems when you try that next.
http://www.15seconds.com/Issue/020102.htm
Happy Coding! --Michael
Michael
Thanks for your comments.
I originally had the add images in the OnLoad, however at this point
the postback information has not been populated. For example i have a
button on the form that moves to the next image, to do this the
CurrentImage property is incremented in the Button.Click event
handler.
This property is not available with the updated value until the
PreRender event. I know the PreRender is too late for adding event
handlers for the dynamically created ImageButtons, but the Page_Load
is too early to get the ViewState properties.
I know i am missing the point somewhere but been suffering these sorts
of problems since trying to take advantage of postbacks rather than
the querystring approach.
The article you pointed me to is very interesting, i actually refered
to it extensively prior to my original posting, however it does not
relate to custom web controls.
Thanks
Blu This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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