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Persist custom object

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fawkes

fawkes

Technical User
Sep 12, 2003
343
GB
I'm new to asp.net and Im using Visual Web Developer Express Edition 2005 (asp.net 2.0)

I've written a class in vb.net using .net 2.0 and want to use it in a web control but whenever the page posts back the web control resets itself.

How do I get around this?
 
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If it's a dynamically added user control, you will have to create it each time the page loads.

Also, if you want to persist data, have a look at adding the relevant information to ViewState.


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Also, if you want to persist data, have a look at adding the relevant information to ViewState.
Click to expand...

I'm new to asp.net, is there a web site that'll explain viewstate?
 
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OK

Looked at the two websites, thanks for your help.

I now realise I need to understand viewstate and serialisation, what would be great is if there is a walkthrough anywhere out there.
 
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Doing my head in now

Here's my custom control

Code: 
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Text
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Runtime.Serialization

''' <summary>
''' Delegate to control the WebDimensionInterface events
''' </summary>
''' <param name="sender"></param>
''' <remarks></remarks>
Public Delegate Sub WebControlEventDelegate( _
                    ByVal sender As EngineeringDimensions.WebDimensionInterface)


<DefaultProperty("Text"), ToolboxData("<{0}:WebDimensionInterface runat=server></{0}:WebDimensionInterface>")> _
<Serializable()> _
Public Class WebDimensionInterface
    Inherits WebControl

#Region " Events "

    Private m_SerializableHandlers As New Generic.List(Of WebControlEventDelegate)
    Private m_NonSerializableHandlers As New Generic.List(Of WebControlEventDelegate)

    Public Custom Event ControlValuesChanged As WebControlEventDelegate
        AddHandler(ByVal value As WebControlEventDelegate)
            If value.Target.GetType.IsSerializable Then
                Me.m_SerializableHandlers.Add(value)
            Else
                Me.m_NonSerializableHandlers.Add(value)
            End If
        End AddHandler

        RemoveHandler(ByVal value As WebControlEventDelegate)
            If value.Target.GetType.IsSerializable Then
                Me.m_SerializableHandlers.Remove(value)
            Else
                Me.m_NonSerializableHandlers.Remove(value)
            End If

        End RemoveHandler

        RaiseEvent(ByVal sender As WebDimensionInterface)

            For Each item As WebControlEventDelegate In Me.m_SerializableHandlers
                item.Invoke(sender)
            Next

            For Each item As WebControlEventDelegate In Me.m_NonSerializableHandlers
                item.Invoke(sender)
            Next

        End RaiseEvent
    End Event

#End Region 'Events 

#Region " Child Controls "

    Private WithEvents m_DimensionLabel As System.Web.UI.WebControls.Label
    Private WithEvents m_MagnitudeTextBox As System.Web.UI.WebControls.TextBox
    Private WithEvents m_UnitsComboBox As System.Web.UI.WebControls.DropDownList
    Private WithEvents m_DirectionTextBox As System.Web.UI.WebControls.TextBox
    Private WithEvents m_DirectionUnitsComboBox As System.Web.UI.WebControls.DropDownList

    Protected Overrides Sub CreateChildControls()

        'Add the child controls

        'Preset the text values
        Me.m_DimensionLabel.Text = Me.DimensionLabelText
        Me.m_MagnitudeTextBox.Text = "0"
        Me.m_DirectionTextBox.Text = "0"

        'Set the widths of the controls
        Me.m_DimensionLabel.Width = 100
        Me.m_MagnitudeTextBox.Width = 100
        Me.m_UnitsComboBox.Width = 100
        Me.m_DirectionTextBox.Width = 100
        Me.m_DirectionUnitsComboBox.Width = 100

        'Add the controls
        Me.Controls.Add(Me.m_DimensionLabel)
        Me.Controls.Add(Me.m_MagnitudeTextBox)
        Me.Controls.Add(Me.m_UnitsComboBox)
        Me.Controls.Add(Me.m_DirectionTextBox)
        Me.Controls.Add(Me.m_DirectionUnitsComboBox)

    End Sub

#End Region 'Child Controls 

#Region " Child Control Dimensions "

    Public Property LabelWidth() As System.Web.UI.WebControls.Unit
        Get
            Return Me.m_DimensionLabel.Width
        End Get
        Set(ByVal value As System.Web.UI.WebControls.Unit)
            Me.m_DimensionLabel.Width = value
        End Set
    End Property

    Public Property MagnitudeWidth() As System.Web.UI.WebControls.Unit
        Get
            Return Me.m_MagnitudeTextBox.Width
        End Get
        Set(ByVal value As System.Web.UI.WebControls.Unit)
            Me.m_MagnitudeTextBox.Width = value
        End Set
    End Property

    Public Property MagnitudeUnitsWidth() As System.Web.UI.WebControls.Unit
        Get
            Return Me.m_UnitsComboBox.Width
        End Get
        Set(ByVal value As System.Web.UI.WebControls.Unit)
            Me.m_UnitsComboBox.Width = value
        End Set
    End Property

    Public Property DirectionWidth() As System.Web.UI.WebControls.Unit
        Get
            Return Me.m_DirectionTextBox.Width
        End Get
        Set(ByVal value As System.Web.UI.WebControls.Unit)
            Me.m_DirectionTextBox.Width = value
        End Set
    End Property

    Public Property DirectionUnitsWidth() As System.Web.UI.WebControls.Unit
        Get
            Return Me.m_DirectionUnitsComboBox.Width
        End Get
        Set(ByVal value As System.Web.UI.WebControls.Unit)
            Me.m_DirectionUnitsComboBox.Width = value
        End Set
    End Property


#End Region

#Region " Child Control Enabled "

    Public Property MagnitudeEnabled() As Boolean
        Get
            Return Me.m_MagnitudeTextBox.Enabled
        End Get
        Set(ByVal value As Boolean)
            Me.m_MagnitudeTextBox.Enabled = value
        End Set
    End Property

    Public Property MagitudeUnitsEnabled() As Boolean
        Get
            Return Me.m_UnitsComboBox.Enabled
        End Get
        Set(ByVal value As Boolean)
            Me.m_UnitsComboBox.Enabled = value
        End Set
    End Property

    Public Property DirectionEnabled() As Boolean
        Get
            Return Me.m_DirectionTextBox.Enabled
        End Get
        Set(ByVal value As Boolean)
            Me.m_DirectionTextBox.Enabled = value
        End Set
    End Property

    Public Property DirectionUnitsEnabled() As Boolean
        Get
            Return Me.m_DirectionUnitsComboBox.Enabled
        End Get
        Set(ByVal value As Boolean)
            Me.m_DirectionUnitsComboBox.Enabled = value
        End Set
    End Property

#End Region 'Child Control Enabled 

#Region " Public Properties "


    Private m_DimensionLabelText As String
    Public Property DimensionLabelText() As String
        Get
            Return Me.m_DimensionLabelText
        End Get
        Set(ByVal value As String)
            Me.m_DimensionLabelText = value
            If Not Me.m_DimensionLabel Is Nothing Then
                Me.m_DimensionLabel.Text = value
            End If
        End Set
    End Property


#End Region 'Public Properties 

    <Bindable(True), Category("Appearance"), DefaultValue(""), Localizable(True)> Property Text() As String
        Get
            Dim s As String = CStr(ViewState("Text"))
            If s Is Nothing Then
                Return String.Empty
            Else
                Return s
            End If
        End Get

        Set(ByVal Value As String)
            ViewState("Text") = Value
        End Set
    End Property

    Protected Overrides Sub RenderContents(ByVal output As HtmlTextWriter)
        EnsureChildControls()
        RenderChildren(output)
    End Sub

    Public Sub New()

        'Initialise the child controls
        Me.m_DimensionLabel = New System.Web.UI.WebControls.Label
        Me.m_MagnitudeTextBox = New System.Web.UI.WebControls.TextBox
        Me.m_UnitsComboBox = New System.Web.UI.WebControls.DropDownList
        Me.m_DirectionTextBox = New System.Web.UI.WebControls.TextBox
        Me.m_DirectionUnitsComboBox = New System.Web.UI.WebControls.DropDownList


    End Sub

#Region " Child Changes Events "

    Private Sub m_MagnitudeTextBox_TextChanged(ByVal sender As Object, _
                                                ByVal e As System.EventArgs) _
                                                    Handles m_MagnitudeTextBox.TextChanged
        RaiseEvent ControlValuesChanged(Me)

    End Sub

    Private Sub m_DirectionTextBox_TextChanged(ByVal sender As Object, _
                                                ByVal e As System.EventArgs) _
                                                    Handles m_DirectionTextBox.TextChanged
        RaiseEvent ControlValuesChanged(Me)

    End Sub

    Private Sub m_UnitsComboBox_SelectedIndexChanged(ByVal sender As Object, _
                                            ByVal e As System.EventArgs) _
                                            Handles m_UnitsComboBox.SelectedIndexChanged

        'Raise the controls changed event
        RaiseEvent ControlValuesChanged(Me)

    End Sub

    Private Sub m_DirectionUnitsComboBox_SelectedIndexChanged(ByVal sender As Object, _
                                            ByVal e As System.EventArgs) _
                                            Handles m_DirectionUnitsComboBox.SelectedIndexChanged

        RaiseEvent ControlValuesChanged(Me)

    End Sub

#End Region 'Child Changes Events 

End Class

In my default asp page I have the following code:

Code: 
Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not Me.Page.IsPostBack Then
            ViewState.Add("mytext", "randomtext")
            ViewState.Add(Me.WebDimensionInterface1.ID, Me.WebDimensionInterface1)
        End If
    End Sub

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Me.Label1.Text = Me.ViewState("mytext")
    End Sub
End Class

The page has an instance of my custom control, a button and a label but I keep getting the message that the custom control is not marked as serializable.

But it is, and I've set the event handler as shown at
I can't see what else to do
 
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