ViewState of Child Controls Not Working Mystery??? -- asp.net webcontrols

Earl Teigrob
10/8/2004 8:15:05 AM

Robert, Thanks for your response. I am doing some more research into this
issue and have modified the code to be, what I believe, is closer to the
solution. In the following code, I override the saveviewstate and
loadviewstate methods (as you suggest) to create the regenerated controls
before viewstate is run.

Earl

I am building a custom control that I want to server as a container for child
controls that can be dynamically added to this control. I can persist the
child controls that are added to my custom control but can to get them to
retain view state.

Below is a striped down version of my control. It exposes one property of
type System.Web.UI.Control that the containing page my set with a dynamically
created control My custom control will then add it to its control tree and
render it to the display. The information need to recreate the control is
stored in a System.Web.UI.Triplet object. On postback, the child control is
reinstanced and given its origonal id and added to the Custom Controls
control tree and rendered to the display.

The only problem is that the ViewState for the child control is not being
retained.

Has anyone solved this puzzle???

Thanks for your help

Earl

CUSTOM WEB SERVER CONTROL

Imports System.ComponentModel
Imports System.Web.UI

<ToolboxData("<{0}:TabMenuA runat=server></{0}:TabMenuA>")> Public Class
ContainerControl
Inherits System.Web.UI.WebControls.WebControl

#Region "Declarations"

Private _ChildControlToRender As System.Web.UI.Control

#End Region

#Region "Properties"

<Bindable(True), Category("Data"), DefaultValue("")> Public Property
ChildControlToRender() As System.Web.UI.Control
Get
Return _ChildControlToRender
End Get
Set(ByVal Value As System.Web.UI.Control)
_ChildControlToRender = Value
End Set
End Property

#End Region

#Region "Methods"

Protected Overrides Sub CreateChildControls()
If Not Page.IsPostBack Then
Controls.Add(_ChildControlToRender)
End If

End Sub

Protected Overrides Sub LoadViewState(ByVal savedState As Object)
Dim objViewStates() As Object
objViewStates = CType(savedState, Object())
Dim Trip As System.Web.UI.Triplet
Trip = objViewStates(1)
_ChildControlToRender = Activator.CreateInstance(CType(Trip.Second,
System.Type))
_ChildControlToRender.ID = Trip.First
Me.Controls.Add(_ChildControlToRender)
MyBase.LoadViewState(objViewStates(0))
End Sub

Protected Overrides Function SaveViewState() As Object
Dim objViewStates(1) As Object
Dim Trip As New System.Web.UI.Triplet
Trip.First = _ChildControlToRender.ID
Trip.Second = _ChildControlToRender.GetType
Trip.Third = Me.ID
objViewStates(1) = Trip
objViewStates(0) = MyBase.SaveViewState()
Return objViewStates
End Function

#End Region
End Class

CONTAINING PAGE CODE

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
If Not Page.IsPostBack Then
Dim myButton As Button = New Button
myButton.Text = "Hello1"
myButton.ID = "ButtonA"
myButton.EnableViewState = True
ContainerControl1.ChildControlToRender = myButton
End If

End Sub

[quoted text, click to view]

Robert Koritnik
10/8/2004 3:55:30 PM

Why don't you override the Save and load viewstate methods while you have to
do everything based on viewstate values.

I didn't exactly get the whole picture why and when you're doing something,
but You should be aware of how exactly ViewState works. Create child
controls happens before PageLoad, when view state is dispatched to controls,
so things should be ok. As I have said. Maybe I didn't get the picture.

Why don't you use Debug.WriteLine method calls to actually se what's going
on in what order and writing information about your vital properties and
method names that write the data to debug output window?

--
RobertK
{ Clever? No just smart. }

[quoted text, click to view]

q NO[at]SPAM q.com
10/8/2004 11:02:28 PM

The problem is in the following code:
Protected Overrides Sub CreateChildControls()
If Not Page.IsPostBack Then
Controls.Add(_ChildControlToRender)
End If

End Sub

change this to:
Protected Overrides Sub CreateChildControls()
Controls.Add(_ChildControlToRender)

If Not Page.IsPostBack Then
End If
End Sub

I had the same problem when programatically
created DataGrid controls. Saw this solution somewhere.
Do not recall exactly where though.
BTW: I can have 0...N data grids created this way on a page.

protected System.Web.UI.WebControls.PlaceHolder PlaceHolder1;
private void Page_Load(object sender, System.EventArgs e)
{
InitDataGrid ();
if (!IsPostBack)
{
}
}
protected void InitDataGrid ()
{
DataGrid gridData;
gridData = new DataGrid();
PlaceHolder1.Controls.Add(gridData);
}

[quoted text, click to view]

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asp.net webcontrols : ViewState of Child Controls Not Working Mystery???