problems with postbacks events from dynamic controls in ASP.Net

Question

I am currently working on a page that has a user control that builds a dynamic table. The control is originally loaded on the Page_Init event, and any time that an event is raised that changes the dynamic control the table is reloaded. The problem here is that if the control is changed between between loads, the events from the control do not fire. For instance, there are originally two rows in the table. An item is added to the table during the postback and now there are four rows (this table adds two rows at a time). Each row has one or two buttons. When the page is loaded and sent back to the browser, if a user clicks on any of the buttons, a postback occurs, but the event does not fire. What am I doing wrong here? How can I tell what control/event caused the postback? Below is the code for both the page, and the user control.

Payments.aspx:

Partial Public Class Payments
Inherits BasePage

Private foodMaster As Food
Private _check As BusinessLayer.CustomerCheck

Private Sub btnAddCheck_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAddCheck.Click
    ' do nothing. the modal window is tied to the button via the modal window in the designer        
End Sub

Private Sub btnCalendar_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles btnCalendar.Click
    calCheckDate.Visible = Not calCheckDate.Visible
    modCheck.Show()
End Sub

Private Sub btnCheckSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnCheckSave.Click
    Try
        If IsNothing(_check) Then _check = New BusinessLayer.CustomerCheck
        If Me.CurrentCheck > 0 Then _check.CheckId = Me.CurrentCheck
        _check.CheckNumber = txtCheckNumber.Text
        _check.CheckDate = CDate(txtCheckDate.Text)
        _check.CheckAmount = CDbl(txtCheckAmount.Text)
        _check.DepositId = Me.CurrentDeposit

        _check.Save()

        LoadControls()
        ' reset the current check to not get confused after an edit
        Me.CurrentCheck = 0
        SetupNewCheck()
    Catch ex As Exception
        lblMessage.Text = "Could not save check."
        lblMessage.Visible = True
        modCheck.Show()
    End Try
End Sub

Private Sub calCheckDate_SelectionChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles calCheckDate.SelectionChanged
    txtCheckDate.Text = calCheckDate.SelectedDate.ToShortDateString()
    calCheckDate.Visible = False
    modCheck.Show()
End Sub

Private Sub cvFutureDate_ServerValidate(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs) Handles cvFutureDate.ServerValidate
    Try
        Dim depositDate As DateTime = DateTime.Parse(txtCheckDate.Text)
        Dim futureDate As DateTime = Now.AddDays(1)
        Dim tomorrow As New DateTime(futureDate.Year, futureDate.Month, futureDate.Day)

        args.IsValid = CBool(depositDate < tomorrow)
    Catch
        args.IsValid = False
    End Try
End Sub

Private Sub cvInvalidAmount_ServerValidate(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs) Handles cvInvalidAmount.ServerValidate
    Try
        Double.Parse(txtCheckAmount.Text)
    Catch
        args.IsValid = False
    End Try
End Sub

Private Sub cvInvalidDate_ServerValidate(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs) Handles cvInvalidDate.ServerValidate
    Try
        DateTime.Parse(txtCheckDate.Text)
    Catch
        args.IsValid = False
    End Try
End Sub

Private Sub DepositEditing()
    foodMaster.Deposit.Load(Me.CurrentDeposit)
    foodMaster.ShowDepositWindow()
End Sub

Private Sub DepositSaved()
    dihHeader.Deposit.Load(Me.CurrentDeposit)
    dihHeader.Reload()
End Sub

Private Sub Payments_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
    LoadControls()
End Sub

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    foodMaster = DirectCast(Me.Master, Food)
    AddHandler foodMaster.SaveClicked, AddressOf DepositSaved
    AddHandler foodMaster.EditButtonClicked, AddressOf DepositEditing

    If IsPostBack = False Then
        Me.CurrentCheck = 0
        SetupNewCheck()
    End If
End Sub

Private Sub pcPayments_ApplyFundsClicked(ByVal CheckId As Integer) Handles pcPayments.ApplyFundsClicked

End Sub

Private Sub pcPayments_DeleteClicked(ByVal CheckId As Integer) Handles pcPayments.DeleteClicked
    Try
        If Me.CurrentCheck = CheckId Then Me.CurrentCheck = 0
        _check = New BusinessLayer.CustomerCheck
        _check.CheckId = CheckId
        _check.DeleteAllPayments()
        _check.Delete()

        LoadControls()
    Catch

    End Try
End Sub

Private Sub pcPayments_EditClicked(ByVal CheckId As Integer) Handles pcPayments.EditClicked
    Me.CurrentCheck = CheckId
    _check = New BusinessLayer.CustomerCheck(CheckId)

    txtCheckAmount.Text = _check.CheckAmount.ToString("0.00")
    txtCheckDate.Text = _check.CheckDate.ToShortDateString
    calCheckDate.SelectedDate = _check.CheckDate
    txtCheckNumber.Text = _check.CheckNumber

    modCheck.Show()
End Sub

Private Sub LoadControls()
    Dim checks As New BusinessLayer.CustomerCheckCollection()
    checks.LoadByDeposit(Me.CurrentDeposit)
    pcPayments.Checks = checks
    pcPayments.Reload()

    dihHeader.Deposit.Load(Me.CurrentDeposit)
    dihHeader.TotalCheckAmount = pcPayments.TotalCheckAmount
    dihHeader.TotalAppliedAmount = pcPayments.TotalAmountApplied
    dihHeader.Reload()
End Sub

Private Sub SetupNewCheck()
    _check = Nothing
    txtCheckDate.Text = Now.ToShortDateString()
    calCheckDate.SelectedDate = Now

    txtCheckAmount.Text = String.Empty
    txtCheckNumber.Text = String.Empty
End Sub

End Class

PaymentsControl.ascx

Public Partial Class PaymentsControl
Inherits System.Web.UI.UserControl

Private _checks As BusinessLayer.CustomerCheckCollection
Private _applied As Double

Public Event ApplyFundsClicked(ByVal CheckId As Integer)
Public Event DeleteClicked(ByVal CheckId As Integer)
Public Event EditClicked(ByVal CheckId As Integer)

Public Sub New()
    _checks = New BusinessLayer.CustomerCheckCollection
    _applied = 0
End Sub

Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    'If IsPostBack = False Then
    '    BindChecks()
    'End If
End Sub

Private Sub ApplyButtonClicked(ByVal sender As Object, ByVal e As EventArgs)
    RaiseEvent ApplyFundsClicked(DirectCast(sender, LinkButton).CommandArgument)
End Sub

Private Sub DeleteButtonClicked(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs)
    RaiseEvent DeleteClicked(DirectCast(sender, ImageButton).CommandArgument)
End Sub

Private Sub EditButtonClicked(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs)
    RaiseEvent EditClicked(DirectCast(sender, ImageButton).CommandArgument)
End Sub

Private Sub BindChecks()
    tblChecks.Rows.Clear()
    tblChecks.Rows.Add(BuildTableHeader())

    _applied = 0

    For i As Int16 = 0 To _checks.Count - 1
        _checks(i).LoadAllPayments()
        _applied += _checks(i).TotalAmountApplied

        tblChecks.Rows.Add(BuildCheckRow(_checks(i)))
        tblChecks.Rows.Add(BuildInvoiceRow(_checks(i)))
    Next

    If tblChecks.Rows.Count = 1 Then tblChecks.Visible = False
End Sub

Private Function BuildCheckRow(ByVal Check As BusinessLayer.CustomerCheck) As TableRow
    Dim checkNumberCell As New TableCell()
    Dim checkDateCell As New TableCell()
    Dim checkAmountCell As New TableCell()
    Dim totalAppliedCell As New TableCell()

    checkNumberCell.Text = Check.CheckNumber
    checkDateCell.Text = Check.CheckDate.ToShortDateString()
    checkAmountCell.Text = Check.CheckAmount.ToString("C")
    totalAppliedCell.Text = Check.TotalAmountApplied.ToString("C")
    If Check.TotalAmountApplied <> Check.CheckAmount Then totalAppliedCell.ForeColor = Drawing.Color.Red

    Dim myRow As New TableRow
    myRow.Cells.Add(BuildCheckControlCell(Check.CheckId))
    myRow.Cells.Add(checkNumberCell)
    myRow.Cells.Add(checkDateCell)
    myRow.Cells.Add(checkAmountCell)
    myRow.Cells.Add(totalAppliedCell)

    Return myRow
End Function

Private Function BuildCheckControlCell(ByVal CheckId As Integer) As TableCell
    Dim editButton As New ImageButton()
    editButton.CommandArgument = CheckId
    editButton.CausesValidation = False
    editButton.AlternateText = "Edit"
    editButton.ImageUrl = "~/images/icons/bullet_edit.png"
    AddHandler editButton.Click, AddressOf EditButtonClicked

    Dim deleteButton As New ImageButton
    deleteButton.CommandArgument = CheckId
    deleteButton.CausesValidation = False
    deleteButton.AlternateText = "Delete"
    deleteButton.ImageUrl = "~/images/icons/bullet_cross.png"
    deleteButton.Attributes.Add("onclick", "return confirmDelete()")
    AddHandler deleteButton.Click, AddressOf DeleteButtonClicked

    Dim blankSpace As New Literal()
    blankSpace.Text = "&nbsp;"

    Dim myCell As New TableCell
    myCell.Controls.Add(editButton)
    myCell.Controls.Add(blankSpace)
    myCell.Controls.Add(deleteButton)

    Return myCell
End Function

Private Function BuildInvoiceRow(ByVal Check As BusinessLayer.CustomerCheck) As TableRow
    Dim invoiceDetailCell As New TableCell
    invoiceDetailCell.ColumnSpan = 4
    invoiceDetailCell.Controls.Add(BuildInvoiceDetailTable(Check.Payments))

    Dim myRow As New TableRow
    myRow.Cells.Add(BuildInvoiceControlCell(Check.CheckId))
    myRow.Cells.Add(invoiceDetailCell)

    Return myRow
End Function

Private Function BuildInvoiceControlCell(ByVal CheckId As Integer) As TableCell
    Dim text As New Literal
    text.Text = "Invoices for check:<br />"

    Dim applyButton As New LinkButton
    applyButton.CommandArgument = CheckId
    applyButton.CausesValidation = False
    applyButton.Text = "Apply Funds"
    AddHandler applyButton.Click, AddressOf ApplyButtonClicked

    Dim myCell As New TableCell
    myCell.Controls.Add(text)
    myCell.Controls.Add(applyButton)

    Return myCell
End Function

Private Function BuildInvoiceDetailTable(ByVal Payments As BusinessLayer.PaymentTransactionCollection) As Table
    Dim myTable As New Table
    myTable.CssClass = "tableSub"
    myTable.CellPadding = "0"
    myTable.CellSpacing = "0"
    myTable.BorderWidth = "0"
    myTable.Rows.Add(BuildInvoiceDetailHeader())

    For i As Integer = 0 To Payments.Count - 1
        myTable.Rows.Add(BuildPaymentRow(Payments(i)))
    Next

    If myTable.Rows.Count = 1 Then myTable.Visible = False

    Return myTable
End Function

Private Function BuildInvoiceDetailHeader() As TableRow
    Dim customerCell As New TableHeaderCell
    Dim invoiceCell As New TableHeaderCell
    Dim dueCell As New TableHeaderCell
    Dim paymentCell As New TableHeaderCell

    customerCell.Text = "Customer"
    invoiceCell.Text = "Invoice number"
    dueCell.Text = "Amount due"
    paymentCell.Text = "Payment amount"

    Dim myRow As New TableRow
    myRow.Cells.Add(customerCell)
    myRow.Cells.Add(invoiceCell)
    myRow.Cells.Add(dueCell)
    myRow.Cells.Add(paymentCell)

    Return myRow
End Function

Private Function BuildPaymentRow(ByVal Payment As BusinessLayer.PaymentTransaction) As TableRow
    Dim customerCell As New TableCell
    Dim invoiceCell As New TableCell
    Dim amountDueCell As New TableCell
    Dim paymentCell As New TableCell

    'Payment.Customer.Load()
    customerCell.Text = Payment.Customer.NumberAndName
    invoiceCell.Text = Payment.Invoice.InvoiceNumber
    amountDueCell.Text = Payment.Invoice.AmountDue.ToString("C")
    paymentCell.Text = Payment.PaymentAmount.ToString("C")

    Dim myRow As New TableRow
    myRow.Cells.Add(customerCell)
    myRow.Cells.Add(invoiceCell)
    myRow.Cells.Add(amountDueCell)
    myRow.Cells.Add(paymentCell)

    Return myRow
End Function

Private Function BuildTableHeader() As TableRow
    Dim blankCell As New TableHeaderCell()
    Dim checkNumberCell As New TableHeaderCell()
    Dim checkDateCell As New TableHeaderCell()
    Dim checkAmountCell As New TableHeaderCell()
    Dim totalUnappliedCell As New TableHeaderCell()

    checkNumberCell.Text = "Check number"
    checkDateCell.Text = "Check date"
    checkAmountCell.Text = "Check amount"
    totalUnappliedCell.Text = "Total unapplied"

    Dim myRow As New TableRow
    myRow.Cells.Add(blankCell)
    myRow.Cells.Add(checkNumberCell)
    myRow.Cells.Add(checkDateCell)
    myRow.Cells.Add(checkAmountCell)
    myRow.Cells.Add(totalUnappliedCell)

    Return myRow
End Function

Public Sub Reload()
    BindChecks()
End Sub

Public Property Checks() As BusinessLayer.CustomerCheckCollection
    Get
        Return _checks
    End Get
    Set(ByVal value As BusinessLayer.CustomerCheckCollection)
        _checks = value
    End Set
End Property

Public ReadOnly Property TotalCheckAmount() As Double
    Get
        Return _checks.TotalCheckAmount
    End Get
End Property

Public ReadOnly Property TotalAmountApplied() As Double
    Get
        Return _applied
    End Get
End Property

End Class

Answer 1

You need to assign the Id property to each dynamically added server control that will serve up postback events. Also, on postback, I believe that the dynamically added controls need to be recreated with the same id in order for postback methods and viewstate to function correctly.