NullReference Error in data acces

Hello,

I'm trying to solve this problem for days but I can't figure out where i'm going wrong.

I have written two classes to retrieve data from a SQL Server database; ContentDB.vb and ContentDetails.vb.

In ContentDB there are, amongst others, two methods, GetMainMenu and GetContent.

GetMainMenu gives a list of items and works great. When I try to use GetContent (which should get me 1 single result) from codebehind, I get a NullReferenceException error.

My code in ContentDB:

Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.Configuration
Imports DataPackage.CMS

Namespace DataUtility.CMS

    Public Class ContentDB
        Private connectionString As String
        Public Sub New()
            ' De standaard connectionstring ophalen
            connectionString = WebConfigurationManager.ConnectionStrings("csPlantRepository").ConnectionString
        End Sub
        Public Sub New(ByVal connectionString As String)
            ' een specifieke connectiestring ophalen
            Me.connectionString = connectionString
        End Sub
        Public Function GetMainMenu(ByVal SiteID As Integer) As List(Of ContentDetails)
            Dim conn As New SqlConnection(connectionString)
            Dim cmd As New SqlCommand("SELECT [contentID], [titel], [ouderID], [siteID], [auteur], [url], [volgnummer] FROM [CMS_Content] WHERE (([siteID] = 1) AND ([ouderID] = 0)) ORDER BY [volgnummer]", conn)
            cmd.CommandType = CommandType.Text
            'cmd.Parameters.Add(New SqlParameter("@siteID", SqlDbType.Int, 4))
            'cmd.Parameters("@siteID").Value = SiteID
            'cmd.Parameters.Add(New SqlParameter("@ouderID", SqlDbType.Int, 4))
            'cmd.Parameters("@ouderID").Value = 0
            Dim menuList As New List(Of ContentDetails)
            Try
                conn.Open()
                Dim reader As SqlDataReader = cmd.ExecuteReader()
                Do While reader.Read()
                    Dim content As New ContentDetails(CInt(reader("contentID")), CStr(reader("titel")), CInt(reader("ouderID")), CInt(reader("siteID")), CStr(reader("auteur")), CStr(reader("url")), CInt(reader("volgnummer")))
                    menuList.Add(content)
                Loop
                reader.Close()
                Return menuList
            Catch ex As Exception

            Finally
                conn.Close()
            End Try
        End Function


        Public Function GetContent(ByVal siteID As Integer) As ContentDetails
            Dim conn As New SqlConnection(connectionString)
            Dim cmd As New SqlCommand("SELECT TOP 1 contentID, titel, ouderID, siteID, auteur, url, volgnummer WHERE siteID = @siteID ORDER BY volgnummer", conn)
            cmd.CommandType = CommandType.Text
            cmd.Parameters.Add(New SqlParameter("@siteID", SqlDbType.Int, 4))
            cmd.Parameters("@siteID").Value = siteID
            Try
                conn.Open()
                Dim reader As SqlDataReader = cmd.ExecuteReader(CommandBehavior.SingleRow)
                reader.Read()
                Dim item As New ContentDetails(CInt(reader("contentID")), CStr(reader("titel")), CInt(reader("ouderID")), CInt(reader("siteID")), CStr(reader("auteur")), CStr(reader("url")), CInt(reader("volgnummer")))
                reader.Close()
                Return item
            Catch ex As Exception

            Finally
                conn.Close()
            End Try
        End Function
    End Class
End Namespace

My code in Codebehind:

Imports System
Imports System.Data
Imports DataPackage.CMS
Imports DataUtility.CMS

Partial Class content
    Inherits System.Web.UI.Page
    Dim websiteID As Integer = "1"
    Dim redirectString As String = "Default.aspx"
    Private db As ContentDB = New ContentDB()
    Private file As ContentDetails = New ContentDetails()

    Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
        websiteID = Request.QueryString("siteID")
        Session("siteID") = 0
        Select Case websiteID
            Case 1
                file = db.GetContent(websiteID)
                Session("siteID") = websiteID
                Dim bestandsnaam As String = file.url.ToString
                redirectString = "iDFM/" & bestandsnaam
                Response.Redirect(redirectString)
            Case 2
                file = db.GetContent(websiteID)
                Session("siteID") = websiteID
                redirectString = "Wiki/" & file.url.ToString
                Response.Redirect(redirectString)
            Case 3
                file = db.GetContent(websiteID)
                Session("siteID") = websiteID
                redirectString = "WSA/" & file.url.ToString
                Response.Redirect(redirectString)
            Case Else
                redirectString = "Account/FoutmeldingWebsite.aspx"
                Response.Redirect(redirectString)
        End Select
    End Sub

End Class

The error is caused bij "file.url.ToString" in the codebehind.

Does anyone have an idea which dumb rookie mistake i'm not seeing?

Thanks, martin