ASP.NET UserControl error - 'is not a member of 'System.Web.UI.UserControl'.'

I have to use an old user control written in the ASP.NET 2.0 days. the control is running fine in a ASP.NET 2.0 environment, but when the control is used with asp.net 4.0 it stops working.

Here is the code from the user control:

<%@ Control Language="VB" Inherits="ControlDb" Src="../Bin/ControlDb.vb"%>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Web" %>
<%@ import Namespace="System.Web.UI" %>
<%@ import Namespace="System.Web.UI.WebControls" %>
<%@ import Namespace="System.Web.UI.HtmlControls" %>
<%@ import Namespace="System.Data.OleDb" %>
<%@ import Namespace="System.Configuration" %>

<script runat="server">
    ' Public isEditable as Boolean

    Public Class CommonDb
        Inherits System.Web.UI.Page
        Dim ConnectionString As String = "<ConnectionString>"

    Public Property dbConnection() As String
        Get
            Return ConnectionString
        End Get
        Set(ByVal Value As String)
            ConnectionString = Value
        End Set
    End Property


    Public Function Execute_GetID(ByVal strSQL As String) As Long
        Dim dbConn As New OleDbConnection(ConnectionString)
        Dim dbComm1 As New OleDbCommand(strSQL, dbConn)
        Dim dbComm2 As New OleDbCommand("SELECT @@IDENTITY", dbConn)
        dbConn.Open()
        dbComm1.ExecuteNonQuery()
        Dim id As Long = CLng(dbComm2.ExecuteScalar())
        Return id
    End Function

    Function Execute(ByVal strSQL As String) As Integer
        Dim dbConn As New OleDbConnection(ConnectionString)
        Dim dbComm As New OleDbCommand(strSQL, dbConn)
        Dim rowsAffected As Integer = 0
        dbComm.Connection = dbConn
        dbConn.Open()
        Try
            rowsAffected = dbComm.ExecuteNonQuery
        Finally
            dbConn.Close()
        End Try
        Return rowsAffected
    End Function

    Public Function FillData(ByVal strSQL As String) As DataSet
        Dim conn As New OleDbConnection(ConnectionString)
        Dim adapter As New OleDbDataAdapter
        Dim ds As New DataSet
        adapter.SelectCommand = New OleDbCommand(strSQL, conn)
        adapter.Fill(ds)
        Return ds
    End Function

End Class


 Private Cdb as new ControlDb()
 Private dtR as DataTable
 Private resourceIds as DataRow()

    Sub Page_Load(Src As Object, E As EventArgs)
    End Sub


Public Sub setData()
dtR = Cdb.FillData("SELECT resourceid FROM VEJLEDNING_RESOURCE WHERE centerid = '" & CenterId & "' AND date='" & DateTime & "' ORDER BY resourceid;").tables(0)
if dtR.rows.count > 0 then
    Dim dtB as DataTable = Cdb.FillData("SELECT Count(resourceid) FROM VEJLEDNING_BOOKING WHERE resourceid='" & dtR.rows(0)("resourceid") & "'").tables(0)
    RBtn.text = FormatDateTime(DateTime,vbShorttime) & "(" & dtR.rows.count & "/" & dtB.rows(0)(0) & ")"  
    RemBtn.Visible=true 
    CType(Page.FindControl("IntervalList"),DropDownList).Enabled=false
    If dtB.rows(0)(0) >= dtR.rows.count
        RBtnClass = "BookingBusyEdit"
    else 
        RBtnClass = "BookingFree"
    end if
else
    RBtn.text = FormatDateTime(DateTime,vbShorttime) & "(0/0)"  
    RBtnClass = "BookingNormalEdit"
    RemBtn.Visible=false
end if
End Sub


Public ReadOnly Property AddBtnId As Button
  Get
    Return AddBtn
  End Get
End Property

Public ReadOnly Property RBtnId As Button
  Get
    Return RBtn
  End Get
End Property

Public ReadOnly Property RemBtnId As Button
  Get
    Return RemBtn
  End Get
End Property

Public Property Text As String
  Get
    Return RBtn.text
  End Get
  Set
    RBtn.text = Value
  End Set
End Property


Public Property DateTime As String
  Get
    Return ViewState("time")
  End Get
  Set
    ViewState("time") = Value
  End Set
End Property

Public Property CenterId As String
  Get
    Return ViewState("centerid")
  End Get
  Set
    ViewState("centerid") = Value
  End Set
End Property

Public Property isEditable As Boolean
  Get
    Return ViewState("isEditable")
  End Get
  Set
    ViewState("isEditable") = Value
  End Set
End Property


Public Property addBtnClass As String
  Get
    Return AddBtn.CssClass
  End Get
  Set
    AddBtn.CssClass = Value
  End Set
End Property

Public Property RBtnClass As String
  Get
    Return RBtn.CssClass
  End Get
  Set
    RBtn.CssClass = Value
  End Set
End Property

Public Property RemBtnClass As String
  Get
    Return RemBtn.CssClass
  End Get
  Set
    RemBtn.CssClass = Value
  End Set
End Property

Sub AddBtn_Click(sender As Object, e As EventArgs)
   NyPost(ViewState("time"))
   setData()
End Sub

Sub RBtn_Click(sender As Object, e As EventArgs)
Dim interval as Integer = CType(Page.FindControl("IntervalList"),DropDownList).SelectedItem.Value
    if isEditable then
        response.redirect("Resource.aspx?id=" & CenterId & "&dtm=" & DateTime & "&interval=" & interval)
    else
        response.redirect("Booking.aspx?id=" & CenterId & "&dtm=" & DateTime)
    end if
End Sub


Sub RemBtn_Click(sender As Object, e As EventArgs)
setData()
Try
    Cdb.Execute("DELETE FROM VEJLEDNING_RESOURCE WHERE centerid = '" & CenterId & "' AND date='" & DateTime & "'") ' Ryd
    'Cdb.Execute("DELETE FROM VEJLEDNING_RESOURCE WHERE resourceid = '" & dtR.rows (dtR.rows.count-1)("resourceid") & "'") ' Fjern sidste
Catch ex As Exception
End Try
setData()
End Sub


Sub NyPost(dato)
Dim strSQL as string
    Dim wn As Integer = DatePart("ww", dato, vbMonday, FirstWeekOfYear.FirstFourDays)
Dim interval as Integer = CType(Page.FindControl("IntervalList"),DropDownList).SelectedItem.Value
If not session("initialer") = nothing then
        if wn = 53 then wn = 1
Try
strSQL = "INSERT INTO VEJLEDNING_RESOURCE ("
strSQL = strSQL & "centerid, "
strSQL = strSQL & "week, "
strSQL = strSQL & "interval, "
strSQL = strSQL & "initialer, "
strSQL = strSQL & "date "
strSQL = strSQL & ") "
strSQL = strSQL & "VALUES ("
strSQL = strSQL & "'" & CenterId & "', " 
strSQL = strSQL & "'" & wn & "', " 
strSQL = strSQL & "'" & interval & "', " 
strSQL = strSQL & "'" & session("initialer") & "', " 
strSQL = strSQL & "'" & dato & "' " 
strSQL = strSQL & ")"
Cdb.Execute(strSQL)
Catch ex As Exception
End Try
End If
End sub

</script>
<table cellpadding="0" cellspacing="0" border="0">
    <tr>
        <td>
            <asp:Button title="Tilføj ressource" id="AddBtn" onclick="AddBtn_Click" CssClass="BookingFree" Visible="true" Width="14px" runat="server" Text="+"></asp:Button>
        </td>
        <td width="100">
            <asp:Button id="RBtn" onclick="RBtn_Click" Width="100px" runat="server"></asp:Button>
        </td>
        <td>
            <asp:Button title="Slet ressource" id="RemBtn" onclick="RemBtn_Click" CssClass="BookingFree" Visible="true" Width="14px" runat="server" Text="-"></asp:Button>
         </td>
    </tr>
</table>

Here is the code from the file that uses the user control:

<%@ Page Language="vb" Inherits="CommonDb" Src="../bin/CommonDb.vb" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Register TagPrefix="MyControls" TagName="RB" Src="ResourceButton.ascx" %>
<script runat="server">
    Dim Cdb As New CommonDb
    Dim ResourceDst As DataTable
    Dim BookingDst As DataTable
    Dim dtmCurrent As Date = Now()
    Dim intDatebuff = (Weekday(dtmCurrent, vbMonday) - 1) * -1
    Dim dtmMonday As Date = FormatDateTime(DateAdd("d", intDatebuff, dtmCurrent), vbShortDate)
    Dim WeekDays As String() = {"Mandag", "Tirsdag", "Onsdag", "Torsdag", "Fredag"}
    Dim dtmStart As String = "08:00"
    Dim dtmEnd As String = "19:00"
    Dim dtmInterval As Integer = 20
    Dim BInterval As String() = {"10", "15", "20", "25", "30", "40", "60"}
    Dim CenterId As String
    Dim cssBtnBar As String
    Dim isEditable As Boolean
    Dim strOverskrift As String
    Dim testYear As String

    Sub Page_Load(ByVal Src As Object, ByVal E As EventArgs)

        Response.Expires = 0
        Response.AppendHeader("Refresh", Convert.ToString((Session.Timeout * 60) + 10) & ";URL=.")
        CenterId = Request.QueryString("id")
        If CenterId <> "" Or Not Session("initialer") Is Nothing Then
            isEditable = (CenterId <> "" And Request.QueryString("admin") <> "" And Not Session("initialer") Is Nothing)
            If Not isEditable Then
                strOverskrift = "Book en tid : "
                cssBtnBar = "display:none;"
        Else
            strOverskrift = "Læg vejledertider ind (" & Session("initialer") & ")"
        End If

        If Not IsPostBack Then
            VisChatBtn(getChat())
            Cdb.Execute("LP_Cleanup_Vejledning_resource") ' 52 uger
            If Request.QueryString("dtm") <> "" Then dtmMonday = Request.QueryString("dtm")
            ShowPage(dtmMonday)
            ViewState("dtmMonday") = dtmMonday
        Else
            dtmMonday = ViewState("dtmMonday")
        End If
    Else
        Response.Redirect(".")
    End If
End Sub

Sub AddControl(ByVal day As String, ByVal e As RepeaterItemEventArgs)
    'Dim uc = CType(e.Item.FindControl(day), Web.UI.UserControl)
    Dim uc As Web.UI.UserControl = e.Item.FindControl(day)
    Dim strTider As String = e.Item.DataItem(day).ToString
    Dim ResourceRows As DataRow() = ResourceDst.Select("date='" & strTider & "'")
    Dim rc As Integer = ResourceRows.Length
    Dim BookingRows As DataRow() = BookingDst.Select("date='" & strTider & "'")
    Dim br As Integer = BookingRows.Length

    If isEditable Then
        uc.RBtnId.text = FormatDateTime(e.Item.DataItem(day).ToString, vbShortTime) & "(" & rc & "/" & br & ")"
        If rc = 0 Then
            uc.RemBtnId.Visible = False
            uc.RBtnClass = "BookingNormalEdit"
        ElseIf br >= rc Then
            uc.RBtnClass = "BookingBusyEdit"
        Else
            uc.RBtnClass = "BookingFree"
        End If
    Else
        uc.RBtnId.text = FormatDateTime(e.Item.DataItem(day).ToString, vbShortTime)
        uc.RemBtnId.Visible = False
        uc.AddBtnId.Visible = False
        If rc = 0 Then
            setNormalBooking(uc, FormatDateTime(e.Item.DataItem(day).ToString, vbShortTime))
        ElseIf br >= rc Then
            uc.RBtnId.Attributes.add("onClick", "this.blur();return false;")
            uc.RBtnClass = "BookingBusy"
        Else
            uc.RBtnClass = "BookingFree"
        End If
    End If

    uc.isEditable = isEditable
    uc.DateTime = strTider
    uc.CenterId = CenterId
End Sub

Here is the error message:

Server Error in '/' Application.
--------------------------------------------------------------------------------

Compilation Error 
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code     appropriately. 

Compiler Error Message: BC30456: 'RBtnId' is not a member of 'System.Web.UI.UserControl'.

Source Error:

Line 209:
Line 210:        If isEditable Then
Line 211:            uc.RBtnId.text = FormatDateTime(e.Item.DataItem(day).ToString, vbShortTime) & "(" & rc & "/" & br & ")"
Line 212:            If rc = 0 Then
Line 213:                uc.RemBtnId.Visible = False

Source File: \\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx Line: 211 


Show Detailed Compiler Output:

Microsoft (R) Visual Basic Compiler version 10.0.30319.233
Copyright (c) Microsoft Corporation.  All rights reserved.

\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(211) : error     BC30456: 'RBtnId' is not a member of 'System.Web.UI.UserControl'.

        uc.RBtnId.text = FormatDateTime(e.Item.DataItem(day).ToString, vbShortTime) & "(" & rc & "/" & br & ")"
             ~~~~~~~~~                                                                                              
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(213) : error BC30456: 'RemBtnId' is not a member of 'System.Web.UI.UserControl'.

            uc.RemBtnId.Visible = False
            ~~~~~~~~~~~                
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(214) : error BC30456: 'RBtnClass' is not a member of 'System.Web.UI.UserControl'.

            uc.RBtnClass = "BookingNormalEdit"
            ~~~~~~~~~~~~                      
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(216) : error BC30456: 'RBtnClass' is not a member of 'System.Web.UI.UserControl'.

            uc.RBtnClass = "BookingBusyEdit"
            ~~~~~~~~~~~~                    
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(218) : error BC30456: 'RBtnClass' is not a member of 'System.Web.UI.UserControl'.

            uc.RBtnClass = "BookingFree"
            ~~~~~~~~~~~~                
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(221) : error BC30456: 'RBtnId' is not a member of 'System.Web.UI.UserControl'.

        uc.RBtnId.text = FormatDateTime(e.Item.DataItem(day).ToString, vbShortTime)
        ~~~~~~~~~                                                                  
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(222) : error BC30456: 'RemBtnId' is not a member of 'System.Web.UI.UserControl'.

        uc.RemBtnId.Visible = False
        ~~~~~~~~~~~                
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(223) : error BC30456: 'AddBtnId' is not a member of 'System.Web.UI.UserControl'.

        uc.AddBtnId.Visible = False
        ~~~~~~~~~~~                
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(227) : error BC30456: 'RBtnId' is not a member of 'System.Web.UI.UserControl'.

            uc.RBtnId.Attributes.add("onClick", "this.blur();return false;")
            ~~~~~~~~~                                                       
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(228) : error BC30456: 'RBtnClass' is not a member of 'System.Web.UI.UserControl'.

            uc.RBtnClass = "BookingBusy"
            ~~~~~~~~~~~~                
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(230) : error BC30456: 'RBtnClass' is not a member of 'System.Web.UI.UserControl'.

            uc.RBtnClass = "BookingFree"
            ~~~~~~~~~~~~                
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(234) : error BC30456: 'isEditable' is not a member of 'System.Web.UI.UserControl'.

    uc.isEditable = isEditable
    ~~~~~~~~~~~~~             
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(235) : error BC30456: 'DateTime' is not a member of 'System.Web.UI.UserControl'.

    uc.DateTime = strTider
    ~~~~~~~~~~~           
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(236) : error BC30456: 'CenterId' is not a member of 'System.Web.UI.UserControl'.

    uc.CenterId = CenterId
    ~~~~~~~~~~~           
\\Webfilefs\websites\DATAPOOL006\u12jbyv\wwwroot\vejlederbooking\hfvuc.aspx(405) : warning BC40004: WithEvents variable 'header' conflicts with property 'header' in the base class 'Page' and should be declared 'Shadows'.

    Protected WithEvents header As Global.System.Web.UI.WebControls.Literal

How do i use this control under 4.0?