I am trying to change a dropdown's value through code on a postback but the
framework seems to override my changes with the value posted. This only
happens when adding controls though code. Here is a code example of the
problem:
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Dim intValue As Integer = 1
intValue = Request.Item("list")
Dim a As New DropDownList
With a
.ID = "list"
.AutoPostBack = True
.EnableViewState = False
.Items.Add(New ListItem("One", 1))
.Items.Add(New ListItem("Two", 2))
.Items.Add(New ListItem("Three", 3))
End With
'change value which should override the posted value
a.SelectedValue = 3
CType(Me.FindControl("Form1"), Object).controls.Add(a)
End Sub
Here is a work around which prevents the framework from matching the control
on post back by changin the control's ID on every post thus preventing the
value override. It works but is ugly and wish someone can show me the
correct to achieve this:
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Dim intValue As Integer = 1
If Not Viewstate("guid") Is Nothing Then
intValue = Request.Item("list" & Viewstate("guid").ToString)
End If
Dim a As New DropDownList
Dim g As Guid
g = Guid.NewGuid
Viewstate("guid") = g
With a
.ID = "list" & g.ToString
.AutoPostBack = True
.EnableViewState = False
.Items.Add(New ListItem("One", 1))
.Items.Add(New ListItem("Two", 2))
.Items.Add(New ListItem("Three", 3))
End With
'change value which overrides the posted value
a.SelectedValue = 3
CType(Me.FindControl("Form1"), Object).controls.Add(a)
End Sub
Thanks
Perry 2 1081
The following MSDN article explains the Control Execution Lifecycle, which
should help you figure out the sequence issue you're having. http://msdn.microsoft.com/library/de...nLifecycle.asp
--
HTH,
Kevin Spencer
..Net Developer
Microsoft MVP
Big things are made up
of lots of little things.
"Perecli Manole" <Pe*****@dslextreme.com> wrote in message
news:#t**************@tk2msftngp13.phx.gbl... I am trying to change a dropdown's value through code on a postback but
the framework seems to override my changes with the value posted. This only happens when adding controls though code. Here is a code example of the problem:
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim intValue As Integer = 1 intValue = Request.Item("list")
Dim a As New DropDownList With a .ID = "list" .AutoPostBack = True .EnableViewState = False .Items.Add(New ListItem("One", 1)) .Items.Add(New ListItem("Two", 2)) .Items.Add(New ListItem("Three", 3)) End With
'change value which should override the posted value a.SelectedValue = 3
CType(Me.FindControl("Form1"), Object).controls.Add(a) End Sub
Here is a work around which prevents the framework from matching the
control on post back by changin the control's ID on every post thus preventing the value override. It works but is ugly and wish someone can show me the correct to achieve this:
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim intValue As Integer = 1 If Not Viewstate("guid") Is Nothing Then intValue = Request.Item("list" & Viewstate("guid").ToString) End If
Dim a As New DropDownList
Dim g As Guid g = Guid.NewGuid Viewstate("guid") = g
With a .ID = "list" & g.ToString .AutoPostBack = True .EnableViewState = False .Items.Add(New ListItem("One", 1)) .Items.Add(New ListItem("Two", 2)) .Items.Add(New ListItem("Three", 3)) End With
'change value which overrides the posted value a.SelectedValue = 3
CType(Me.FindControl("Form1"), Object).controls.Add(a) End Sub Thanks Perry
I have read this article before and does not explain what is occuring here.
The document under the OnLoad states: At this point, server controls in the
tree are created and initialized, the state is restored, and form controls
reflect client-side data.
Well, as you can see from my example, I overwrote the OnLoad event. What do
I need to do to prevent posted values from overitting the values I set in
the OnLoad event.
Perry
"Kevin Spencer" <ks******@takempis.com> wrote in message
news:u%****************@TK2MSFTNGP11.phx.gbl... The following MSDN article explains the Control Execution Lifecycle, which should help you figure out the sequence issue you're having.
http://msdn.microsoft.com/library/de...nLifecycle.asp -- HTH, Kevin Spencer .Net Developer Microsoft MVP Big things are made up of lots of little things.
"Perecli Manole" <Pe*****@dslextreme.com> wrote in message news:#t**************@tk2msftngp13.phx.gbl... I am trying to change a dropdown's value through code on a postback but the framework seems to override my changes with the value posted. This only happens when adding controls though code. Here is a code example of the problem:
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim intValue As Integer = 1 intValue = Request.Item("list")
Dim a As New DropDownList With a .ID = "list" .AutoPostBack = True .EnableViewState = False .Items.Add(New ListItem("One", 1)) .Items.Add(New ListItem("Two", 2)) .Items.Add(New ListItem("Three", 3)) End With
'change value which should override the posted value a.SelectedValue = 3
CType(Me.FindControl("Form1"), Object).controls.Add(a) End Sub
Here is a work around which prevents the framework from matching the control on post back by changin the control's ID on every post thus preventing
the value override. It works but is ugly and wish someone can show me the correct to achieve this:
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim intValue As Integer = 1 If Not Viewstate("guid") Is Nothing Then intValue = Request.Item("list" & Viewstate("guid").ToString) End If
Dim a As New DropDownList
Dim g As Guid g = Guid.NewGuid Viewstate("guid") = g
With a .ID = "list" & g.ToString .AutoPostBack = True .EnableViewState = False .Items.Add(New ListItem("One", 1)) .Items.Add(New ListItem("Two", 2)) .Items.Add(New ListItem("Three", 3)) End With
'change value which overrides the posted value a.SelectedValue = 3
CType(Me.FindControl("Form1"), Object).controls.Add(a) End Sub Thanks Perry
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