Cookie being deleted unexpectedly by the application

Question

I am having an issue with a cookie that keeps getting deleted by the application. When you go into the application, if the cookie does not exist, it gets created. This works fine and everything in the cookie is stored correctly.

When I click on a link to go to another page, once everything loads completely, the cookie gets deleted from the file system. Even stranger than that, the values from the cookie remain until the browser is closed. That is the application appears to be retaining the values even though the cookie does not exist on the local file system. The next time you enter the application, the cookie is recreated so any values stored are lost.

Now, I have done some tweaking on the code to see what could be causing it. I found that I am adding the cookie to the Response object any time I make a change to the cookie. The cookie is also being added to the Response object when the page load is completed. My initial thought was that adding the cookie multiple times to the Response object could be causing the issue. I commented out the code in the page load complete event and the cookie hung around until the next postback. Then I put in some logic to keep the application from putting the cookie into the Response object more than once, and then I lost the cookie again at the same point as before.

All of the code for handling cookies is in my "base page" that all pages inherit from. The page that seems to be loosing the cookie is my search page. I am including the code from both of those pages.

BasePage.vb

Public Class BasePage
Inherits Page
#Region "attributes"
Private _cookie As HttpCookie
Private _savedCookie As Boolean

Private Const COOKIE_NAME As String = "KDOELog"
Private Const COOKIE_COLUMNS As String = "cols"
Private Const COOKIE_SEARCH_BRANCH As String = "b"
Private Const COOKIE_SEARCH_COLLECTOR As String = "c"
Private Const COOKIE_SEARCH_CONF_NUMBER As String = "a"
Private Const COOKIE_SEARCH_NA_NUMBER As String = "n"
Private Const COOKIE_SEARCH_CUST_NUMBER As String = "u"
Private Const COOKIE_SEARCH_INV_NUMBER As String = "i"
Private Const COOKIE_SEARCH_CONTRACT As String = "t"
Private Const COOKIE_SEARCH_ORDER_TYPE As String = "y"
Private Const COOKIE_SEARCH_DSR_NUMBER As String = "r"
Private Const COOKIE_SEARCH_DSM_NUMBER As String = "m"
Private Const COOKIE_SEARCH_EXCEPTION As String = "e"
Private Const COOKIE_SEARCH_START_DATE As String = "s"
Private Const COOKIE_SEARCH_END_DATE As String = "d"
Private Const COOKIE_PAGE_INDEX As String = "pg"
Private Const COOKIE_SORT_COLUMN As String = "sc"
Private Const COOKIE_SORT_DIRECTION As String = "sd"

Private Const SESSION_USER As String = "user"
#End Region

#Region "constructor"
Public Sub New()
    _savedCookie = False
End Sub
#End Region

#Region "events"
Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If IsPostBack = False Then
        ' determines whether or not to show the link for Node Search
        Dim myMaster As Food = DirectCast(Me.Master, Food)
        If AuthenticatedUser.IsCorporateAdmin Or AuthenticatedUser.IsBranchAdmin Then
            myMaster.ShowNodeItemLink = True
        Else
            myMaster.ShowNodeItemLink = False
        End If
    End If
End Sub

Private Sub Page_LoadComplete(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.LoadComplete
    If _savedCookie = False Then Response.Cookies.Add(_cookie)
End Sub

Private Sub Page_PreInit(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreInit
    If IsNothing(Request.Cookies(COOKIE_NAME)) Then
        _cookie = New HttpCookie(COOKIE_NAME)

        _cookie.Expires = New Date(2999, 12, 31)

        _cookie.Values.Add(COOKIE_COLUMNS, GetDefaultColumnList())
        _cookie.Values.Add(COOKIE_SEARCH_BRANCH, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_COLLECTOR, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_CONF_NUMBER, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_NA_NUMBER, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_CUST_NUMBER, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_INV_NUMBER, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_CONTRACT, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_ORDER_TYPE, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_DSR_NUMBER, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_DSM_NUMBER, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_EXCEPTION, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_START_DATE, String.Empty)
        _cookie.Values.Add(COOKIE_SEARCH_END_DATE, String.Empty)
        _cookie.Values.Add(COOKIE_PAGE_INDEX, 0)
        _cookie.Values.Add(COOKIE_SORT_COLUMN, "eback_datetime")
        _cookie.Values.Add(COOKIE_SORT_DIRECTION, SORT_DIRECTION_ASC)

        SaveCookie()
    Else
        _cookie = Request.Cookies(COOKIE_NAME)
    End If

    If IsNothing(Session(SESSION_USER)) Then Session(SESSION_USER) = New User(Context.User.Identity.Name)
End Sub
#End Region

#Region "methods"
Protected Function GetColumnList() As String()
    Return Server.HtmlEncode(_cookie(COOKIE_COLUMNS)).Split(",")
End Function

Private Function GetDefaultColumnList() As String
    ' set the default list of columns
    Dim columnList As New StringBuilder()
    columnList.Append(COL_COLLECTOR).Append(",")
    columnList.Append(COL_CONF_NUM).Append(",")
    columnList.Append(COL_NODE_NUM).Append(",")
    columnList.Append(COL_ORDER_TYPE).Append(",")
    columnList.Append(COL_CUST_NUM).Append(",")
    columnList.Append(COL_ERROR_IND).Append(",")
    columnList.Append(COL_DSR_NUM).Append(",")
    columnList.Append(COL_DSR_NAME).Append(",")
    columnList.Append(COL_DSM_NUM).Append(",")
    columnList.Append(COL_CONTRACT).Append(",")
    columnList.Append(COL_NA_NUM).Append(",")
    columnList.Append(COL_NA_SUB).Append(",")
    columnList.Append(COL_INV_NUM).Append(",")
    columnList.Append(COL_CONF_DATE).Append(",")
    columnList.Append(COL_LINE_ITEMS).Append(",")
    columnList.Append(COL_DELV_DATE).Append(",")
    columnList.Append(COL_SALES_AMT).Append(",")
    columnList.Append(COL_BRANCH)

    Return columnList.ToString()
End Function

Protected Function HasSearchValues() As Boolean
    Return CBool(_cookie(COOKIE_SEARCH_BRANCH) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_COLLECTOR) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_CONF_NUMBER) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_NA_NUMBER) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_CUST_NUMBER) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_INV_NUMBER) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_CONTRACT) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_ORDER_TYPE) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_DSR_NUMBER) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_DSM_NUMBER) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_EXCEPTION) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_START_DATE) > String.Empty Or _
                 _cookie(COOKIE_SEARCH_END_DATE) > String.Empty)
End Function

Protected Sub ResetSearchValues()
    _cookie(COOKIE_SEARCH_BRANCH) = String.Empty
    _cookie(COOKIE_SEARCH_COLLECTOR) = String.Empty
    _cookie(COOKIE_SEARCH_CONF_NUMBER) = String.Empty
    _cookie(COOKIE_SEARCH_NA_NUMBER) = String.Empty
    _cookie(COOKIE_SEARCH_CUST_NUMBER) = String.Empty
    _cookie(COOKIE_SEARCH_INV_NUMBER) = String.Empty
    _cookie(COOKIE_SEARCH_CONTRACT) = String.Empty
    _cookie(COOKIE_SEARCH_ORDER_TYPE) = String.Empty
    _cookie(COOKIE_SEARCH_DSR_NUMBER) = String.Empty
    _cookie(COOKIE_SEARCH_DSM_NUMBER) = String.Empty
    _cookie(COOKIE_SEARCH_EXCEPTION) = String.Empty
    _cookie(COOKIE_SEARCH_START_DATE) = String.Empty
    _cookie(COOKIE_SEARCH_END_DATE) = String.Empty
    _cookie(COOKIE_PAGE_INDEX) = 0
    _cookie(COOKIE_SORT_COLUMN) = "eback_datetime"
    _cookie(COOKIE_SORT_DIRECTION) = SORT_DIRECTION_ASC

    SaveCookie()
End Sub

Protected Sub SaveCookie()
    If _savedCookie = False Then
        Response.Cookies.Add(_cookie)
        _savedCookie = True
    End If
End Sub

Protected Sub SetColumnList(ByVal ColumnList As String)
    _cookie(COOKIE_COLUMNS) = ColumnList

    SaveCookie()
End Sub
#End Region

#Region "properties"
Public ReadOnly Property AuthenticatedUser() As User
    Get
        If IsNothing(Session(SESSION_USER)) Then Session(SESSION_USER) = New User(Context.User.Identity.Name)

        Return DirectCast(Session(SESSION_USER), User)
    End Get
End Property

Public ReadOnly Property UserName() As String
    Get
        Return Context.User.Identity.Name
    End Get
End Property

Public Property SearchBranch() As String
    Get
        Return _cookie(COOKIE_SEARCH_BRANCH)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_BRANCH) = value
    End Set
End Property

Public Property SearchCollector() As String
    Get
        Return _cookie(COOKIE_SEARCH_COLLECTOR)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_COLLECTOR) = value
    End Set
End Property

Public Property SearchConfirmationNumber() As String
    Get
        Return _cookie(COOKIE_SEARCH_CONF_NUMBER)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_CONF_NUMBER) = value
    End Set
End Property

Public Property SearchNationalAccountNumber() As String
    Get
        Return _cookie(COOKIE_SEARCH_NA_NUMBER)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_NA_NUMBER) = value
    End Set
End Property

Public Property SearchCustomerNumber() As String
    Get
        Return _cookie(COOKIE_SEARCH_CUST_NUMBER)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_CUST_NUMBER) = value
    End Set
End Property

Public Property SearchInvoiceNumber() As String
    Get
        Return _cookie(COOKIE_SEARCH_INV_NUMBER)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_INV_NUMBER) = value
    End Set
End Property

Public Property SearchContract() As String
    Get
        Return _cookie(COOKIE_SEARCH_CONTRACT)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_CONTRACT) = value
    End Set
End Property

Public Property SearchOrderType() As String
    Get
        Return _cookie(COOKIE_SEARCH_ORDER_TYPE)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_ORDER_TYPE) = value
    End Set
End Property

Public Property SearchDsrNumber() As String
    Get
        Return _cookie(COOKIE_SEARCH_DSR_NUMBER)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_DSR_NUMBER) = value
    End Set
End Property

Public Property SearchDsmNumber() As String
    Get
        Return _cookie(COOKIE_SEARCH_DSM_NUMBER)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_DSM_NUMBER) = value
    End Set
End Property

Public Property SearchErrorType() As String
    Get
        Return _cookie(COOKIE_SEARCH_EXCEPTION)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_EXCEPTION) = value
    End Set
End Property

Public Property SearchStartDate() As String
    Get
        Return _cookie(COOKIE_SEARCH_START_DATE)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_START_DATE) = value
    End Set
End Property

Public Property SearchEndDate() As String
    Get
        Return _cookie(COOKIE_SEARCH_END_DATE)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SEARCH_END_DATE) = value
    End Set
End Property

Public Property PageIndex() As String
    Get
        Return _cookie(COOKIE_PAGE_INDEX)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_PAGE_INDEX) = value
    End Set
End Property

Public Property SortColumn() As String
    Get
        Return _cookie(COOKIE_SORT_COLUMN)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SORT_COLUMN) = value
    End Set
End Property

Public Property SortDirection() As String
    Get
        Return _cookie(COOKIE_SORT_DIRECTION)
    End Get
    Set(ByVal value As String)
        _cookie(COOKIE_SORT_DIRECTION) = value
    End Set
End Property
#End Region
End Class

Search.aspx.vb

Public Partial Class Search
Inherits BasePage

#Region "attributes"

#End Region

#Region "events"
Private Sub btnColumnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnColumnSave.Click
    Dim columns As New StringBuilder

    If chkCollector.Checked Then columns.Append(COL_COLLECTOR).Append(",")
    If chkAckNumber.Checked Then columns.Append(COL_CONF_NUM).Append(",")
    If chkNodeNumber.Checked Then columns.Append(COL_NODE_NUM).Append(",")
    If chkOrderType.Checked Then columns.Append(COL_ORDER_TYPE).Append(",")
    If chkCustNumber.Checked Then columns.Append(COL_CUST_NUM).Append(",")
    If chkCustName.Checked Then columns.Append(COL_CUST_NAME).Append(",")
    If chkOrderExceptions.Checked Then columns.Append(COL_ERROR_IND).Append(",")
    If chkDsrNumber.Checked Then columns.Append(COL_DSR_NUM).Append(",")
    If chkDsrName.Checked Then columns.Append(COL_DSR_NAME).Append(",")
    If chkDsmNumber.Checked Then columns.Append(COL_DSM_NUM).Append(",")
    If chkDsmName.Checked Then columns.Append(COL_DSM_NAME).Append(",")
    If chkContract.Checked Then columns.Append(COL_CONTRACT).Append(",")
    If chkNationalAcct.Checked Then columns.Append(COL_NA_NUM).Append(",")
    If chkNatAcctSub.Checked Then columns.Append(COL_NA_SUB).Append(",")
    If chkInvoiceNumber.Checked Then columns.Append(COL_INV_NUM).Append(",")
    If chkAckDateTime.Checked Then columns.Append(COL_CONF_DATE).Append(",")
    If chkLineItem.Checked Then columns.Append(COL_LINE_ITEMS).Append(",")
    If chkDeliveryDate.Checked Then columns.Append(COL_DELV_DATE).Append(",")
    If chkSalesAmount.Checked Then columns.Append(COL_SALES_AMT).Append(",")
    If chkBranch.Checked Then columns.Append(COL_BRANCH).Append(",")

    ' remove the last comma from the list
    columns = columns.Remove(columns.Length - 1, 1)

    SetColumnList(columns.ToString())
    SaveCookie()

    ManageGridColumns()
End Sub

Private Sub btnEndDate_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles btnEndDate.Click
    calEndDate.Visible = Not calEndDate.Visible

    If calEndDate.Visible Then
        Try
            calEndDate.SelectedDate = Date.Parse(txtEndDate.Text)
        Catch
            calEndDate.SelectedDate = Now
        End Try
    End If

    modSearch.Show()
End Sub

Private Sub btnSearchReset_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSearchReset.Click
    ddlBranch.SelectedIndex = 0
    SearchBranch = ddlBranch.SelectedValue
    ddlCollectorType.SelectedIndex = 0
    SearchCollector = ddlCollectorType.SelectedValue
    ddlOrderType.SelectedIndex = 0
    SearchOrderType = ddlOrderType.SelectedValue
    ddlErrorCode.SelectedIndex = 0
    SearchErrorType = ddlErrorCode.SelectedValue

    SearchConfirmationNumber = String.Empty
    SearchNationalAccountNumber = String.Empty
    SearchCustomerNumber = String.Empty
    SearchInvoiceNumber = String.Empty
    SearchContract = String.Empty
    SearchDsrNumber = String.Empty
    'SearchDsmNumber = String.Empty
    SetDsmInfo()

    SearchStartDate = Now.ToShortDateString()
    SearchEndDate = Now.ToShortDateString()

    SaveCookie()

    SetSearchWindow()
    modSearch.Show()
End Sub

Private Sub btnSearchSearch_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSearchSearch.Click
    SearchBranch = ddlBranch.SelectedValue
    SearchCollector = ddlCollectorType.SelectedValue
    SearchConfirmationNumber = txtAckNumber.Text
    SearchCustomerNumber = txtCustomerNumber.Text
    SearchInvoiceNumber = txtInvoiceNumber.Text
    SearchDsrNumber = txtDsrNumber.Text
    SearchDsmNumber = txtDsmNumber.Text
    SearchNationalAccountNumber = txtNationalAccountNumber.Text
    SearchContract = txtContract.Text
    SearchErrorType = ddlErrorCode.SelectedValue
    SearchOrderType = ddlOrderType.SelectedValue
    SearchStartDate = txtStartDate.Text
    SearchEndDate = txtEndDate.Text

    SaveCookie()

    PageIndex = 0
    dgResults.CurrentPageIndex = 0
    BindResults()
End Sub

Private Sub btnStartDate_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles btnStartDate.Click
    calStartDate.Visible = Not calStartDate.Visible

    If calStartDate.Visible Then
        Try
            calStartDate.SelectedDate = Date.Parse(txtStartDate.Text)
        Catch
            calStartDate.SelectedDate = Now
        End Try
    End If

    modSearch.Show()
End Sub

Private Sub calEndDate_SelectionChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles calEndDate.SelectionChanged
    txtEndDate.Text = calEndDate.SelectedDate.ToShortDateString()
    calEndDate.Visible = False
    modSearch.Show()
End Sub

Private Sub calStartDate_SelectionChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles calStartDate.SelectionChanged
    txtStartDate.Text = calStartDate.SelectedDate.ToShortDateString()
    calStartDate.Visible = False
    modSearch.Show()
End Sub

Private Sub dgResults_PageIndexChanged(ByVal source As Object, ByVal e As System.Web.UI.WebControls.DataGridPageChangedEventArgs) Handles dgResults.PageIndexChanged
    PageIndex = e.NewPageIndex
    dgResults.CurrentPageIndex = e.NewPageIndex
    BindResults()
End Sub

Private Sub dgResults_SortCommand(ByVal source As Object, ByVal e As System.Web.UI.WebControls.DataGridSortCommandEventArgs) Handles dgResults.SortCommand
    If SortColumn.Equals(e.SortExpression) Then
        If SortDirection = SORT_DIRECTION_ASC Then
            SortDirection = SORT_DIRECTION_DESC
        Else
            SortDirection = SORT_DIRECTION_ASC
        End If
    Else
        SortColumn = e.SortExpression
        SortDirection = SORT_DIRECTION_ASC
    End If

    PageIndex = 0
    dgResults.CurrentPageIndex = 0

    BindResults()
End Sub

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If IsPostBack = False Then
        SetDsmInfo()
        txtStartDate.Text = Now.ToShortDateString()
        txtEndDate.Text = Now.ToShortDateString()

        BindBranches()
        BindCollectorTypes()
        BindTransmissionTypes()
        BindErrorCodes()

        SetupColumnWindow()
        ManageGridColumns()

        If HasSearchValues() Then
            SetSearchWindow()
            dgResults.CurrentPageIndex = CInt(PageIndex)
            BindResults()
        Else
            modSearch.Show()
        End If
    End If
End Sub
#End Region

#Region "methods"
Private Sub BindBranches()
    If AuthenticatedUser.IsCorporateAdmin Then
        Dim branches As New BranchCollection
        branches.Load()

        ddlBranch.DataSource = branches
        ddlBranch.DataTextField = "BranchDescription"
        ddlBranch.DataValueField = "BranchName"
        ddlBranch.DataBind()
    Else
        Dim myBranch As New Branch(AuthenticatedUser.Division)

        ddlBranch.Items.Clear()
        ddlBranch.Items.Add(New ListItem(myBranch.BranchDescription, myBranch.BranchName))
        ddlBranch.Enabled = False
    End If
End Sub

Private Sub BindCollectorTypes()
    Dim types As New OrderTypeCollection
    types.Load()

    ddlCollectorType.DataSource = types
    ddlCollectorType.DataTextField = "eb_order_description"
    ddlCollectorType.DataValueField = "eb_order_type"
    ddlCollectorType.DataBind()
End Sub

Private Sub BindErrorCodes()
    Dim codes As New KDOE_Library.BusinessLayer.ErrorTypeCollection
    codes.Load()

    ddlErrorCode.DataSource = codes
    ddlErrorCode.DataTextField = "eb_error_desc"
    ddlErrorCode.DataValueField = "eb_error_type"
    ddlErrorCode.DataBind()
End Sub

Private Sub BindResults()
    Dim results As New ConfirmationHeaderCollection()
    results.Search(SearchCollector, SearchConfirmationNumber, SearchBranch, SearchCustomerNumber, SearchInvoiceNumber, _
                   SearchDsrNumber, SearchDsmNumber, SearchNationalAccountNumber, SearchContract, SearchErrorType, _
                   SearchOrderType, SearchStartDate, SearchEndDate)

    results.SortExpression = TranslateSortExpression(SortColumn)
    results.SortDirection = IIf(SortDirection.Equals(SORT_DIRECTION_ASC), _
                                ConfirmationHeaderCollection.SortOrder.Ascending, _
                                ConfirmationHeaderCollection.SortOrder.Descending)
    results.Sort(results)

    dgResults.DataSource = results
    dgResults.DataBind()

    lblResultCount.Text = String.Format("{0} records found", results.Count.ToString("#,###,###"))
End Sub

Private Sub BindTransmissionTypes()
    Dim transTypes As New TransTypeCollection
    transTypes.Load()

    ddlOrderType.DataSource = transTypes
    ddlOrderType.DataTextField = "eb_trans_desc"
    ddlOrderType.DataValueField = "eb_trans_type"
    ddlOrderType.DataBind()
End Sub

Private Sub HideAllColumns()
    For i As Integer = 0 To dgResults.Columns.Count - 1
        dgResults.Columns(i).Visible = False
    Next
End Sub

Private Sub ManageGridColumns()
    HideAllColumns()

    Dim columns() As String = GetColumnList()

    For i As Integer = 0 To columns.Length - 1
        Try
            dgResults.Columns(CInt(columns(i))).Visible = True
        Catch
            ' do nothing if an error is detected because it indicates a dirty cookie
        End Try
    Next
End Sub

Private Sub SetupColumnWindow()
    Dim columns() As String = GetColumnList()

    For i As Integer = 0 To columns.Length - 1
        Try
            Select Case CInt(columns(i))
                Case COL_COLLECTOR
                    chkCollector.Checked = True
                Case COL_CONF_NUM
                    chkAckNumber.Checked = True
                Case COL_NODE_NUM
                    chkNodeNumber.Checked = True
                Case COL_ORDER_TYPE
                    chkOrderType.Checked = True
                Case COL_CUST_NUM
                    chkCustNumber.Checked = True
                Case COL_CUST_NAME
                    chkCustName.Checked = True
                Case COL_ERROR_IND
                    chkOrderExceptions.Checked = True
                Case COL_DSR_NUM
                    chkDsrNumber.Checked = True
                Case COL_DSR_NAME
                    chkDsrName.Checked = True
                Case COL_DSM_NUM
                    chkDsmNumber.Checked = True
                Case COL_DSM_NAME
                    chkDsmName.Checked = True
                Case COL_CONTRACT
                    chkContract.Checked = True
                Case COL_NA_NUM
                    chkNationalAcct.Checked = True
                Case COL_NA_SUB
                    chkNatAcctSub.Checked = True
                Case COL_INV_NUM
                    chkInvoiceNumber.Checked = True
                Case COL_CONF_DATE
                    chkAckDateTime.Checked = True
                Case COL_LINE_ITEMS
                    chkLineItem.Checked = True
                Case COL_DELV_DATE
                    chkDeliveryDate.Checked = True
                Case COL_SALES_AMT
                    chkSalesAmount.Checked = True
                Case COL_BRANCH
                    chkBranch.Checked = True
                Case Else
                    ' do nothing
            End Select
        Catch
            ' do nothing because the entry is not an actual column number
            ' i.e. the cookie has dirty data
        End Try
    Next
End Sub

Private Sub SetDsmInfo()
    If AuthenticatedUser.IsDsm Then
        Dim theService As New DsmService.DsmService
        theService.PreAuthenticate = True
        theService.Credentials = New System.Net.NetworkCredential("someuser", "somepassword", "somedomain")

        Dim myDsm As DsmService.Dsm = theService.GetDsmByName(AuthenticatedUser.FirstName, AuthenticatedUser.LastName)
        If IsPostBack Then
            SearchDsmNumber = myDsm.DsmNumber
        Else
            txtDsmNumber.Text = myDsm.DsmNumber
        End If
        txtDsmNumber.Enabled = False
    Else
        'txtDsmNumber.Text = String.Empty
        SearchDsmNumber = String.Empty
        txtDsmNumber.Enabled = True
    End If
End Sub

Private Sub SetSearchWindow()
    Try
        ddlBranch.SelectedValue = SearchBranch
        ddlCollectorType.SelectedValue = SearchCollector
        txtAckNumber.Text = SearchConfirmationNumber
        txtNationalAccountNumber.Text = SearchNationalAccountNumber
        txtCustomerNumber.Text = SearchCustomerNumber
        txtInvoiceNumber.Text = SearchInvoiceNumber
        txtContract.Text = SearchContract
        ddlOrderType.SelectedValue = SearchOrderType
        txtDsrNumber.Text = SearchDsrNumber
        txtDsmNumber.Text = SearchDsmNumber
        ddlErrorCode.SelectedValue = SearchErrorType
        txtStartDate.Text = SearchStartDate
        calStartDate.SelectedDate = CDate(SearchStartDate)
        txtEndDate.Text = SearchEndDate
        calEndDate.SelectedDate = CDate(SearchEndDate)
    Catch
        ' do nothing because an error would be caused by dirty data from the cookie
    End Try
End Sub

Private Function TranslateSortExpression(ByVal SortExpression As String) As ConfirmationHeaderCollection.SortColumn
    Dim retVal As ConfirmationHeaderCollection.SortColumn = ConfirmationHeaderCollection.SortColumn.eback_datetime

    Select Case SortExpression
        Case "ebcollector"
            retVal = ConfirmationHeaderCollection.SortColumn.ebcollector
        Case "eback"
            retVal = ConfirmationHeaderCollection.SortColumn.eback
        Case "ebnode"
            retVal = ConfirmationHeaderCollection.SortColumn.ebnode
        Case "ebordertype"
            retVal = ConfirmationHeaderCollection.SortColumn.ebordertype
        Case "ebcust"
            retVal = ConfirmationHeaderCollection.SortColumn.ebcust
        Case "CustomerName"
            retVal = ConfirmationHeaderCollection.SortColumn.CustomerName
        Case "eberror"
            retVal = ConfirmationHeaderCollection.SortColumn.eberror
        Case "ebslm"
            retVal = ConfirmationHeaderCollection.SortColumn.ebslm
        Case "DsrName"
            retVal = ConfirmationHeaderCollection.SortColumn.DsrName
        Case "DsmNumber"
            retVal = ConfirmationHeaderCollection.SortColumn.DsmNumber
        Case "DsmName"
            retVal = ConfirmationHeaderCollection.SortColumn.DsmName
        Case "ebcontract"
            retVal = ConfirmationHeaderCollection.SortColumn.ebcontract
        Case "ebna"
            retVal = ConfirmationHeaderCollection.SortColumn.ebna
        Case "ebnasub"

Answer 1

I think that I have found the answer. The cookie hasn't been removed in a while, so this looks like it. I tried several other things trying to find the issue, and I had finally given up on finding the solution by tweaking my code, so I took to the internet. It was on MS's website that I found this little gem.

If you do not set the cookie's expiration, the cookie is created but it is not stored on the user's hard disk. Instead, the cookie is maintained as part of the user's session information. When the user closes the browser, the cookie is discarded. A non-persistent cookie like this is useful for information that needs to be stored for only a short time or that for security reasons should not be written to disk on the client computer. For example, non-persistent cookies are useful if the user is working on a public computer, where you do not want to write the cookie to disk.
http://msdn.microsoft.com/en-us/library/ms178194.aspx

So the issue here is the fact that the cookie has an expiration date when the cookie is initially created. However, reading the cookie from the Request object does not include the expiration date. So, I fixed it by setting the expiration date before adding the cookie back to the Response object.