' The LoadSiteMapData() Function loads site navigation
' data from persistent storage into a DataTable.

Dim siteMapData As DataTable
siteMapData = LoadSiteMapData()

' Create a SiteMapNodeCollection.
Dim nodes As New SiteMapNodeCollection()

' Create a SiteMapNode and add it to the collection.
Dim tempNode As SiteMapNode
Dim row As DataRow
Dim index As Integer
index = 0

While (index < siteMapData.Rows.Count)

    row = siteMapData.Rows(index)

    ' Create a node based on the data in the DataRow.
    tempNode = New SiteMapNode(SiteMap.Provider, row("Key").ToString(), row("Url").ToString())

    ' Add the node to the collection.
    nodes.Add(tempNode)
    index = index + 1
End While

Protected Overridable Sub LoadSiteMapFromStore()
    Dim pathToOpen As String
    SyncLock Me
      ' If a root node exists, LoadSiteMapFromStore has already
      ' been called, and the method can return.
      If Not (aRootNode Is Nothing) Then
        Return
      Else
        pathToOpen = HttpContext.Current.Server.MapPath("~" & "\\" & sourceFilename)
        If File.Exists(pathToOpen) Then
          ' Open the file to read from.
          Dim sr As StreamReader = File.OpenText(pathToOpen)
          Try

            ' Clear the state of the collections and aRootNode
            aRootNode = Nothing
            siteMapNodes.Clear()
            childParentRelationship.Clear()

            ' Parse the file and build the site map
            Dim s As String = ""
            Dim nodeValues As String() = Nothing
            Dim temp As SiteMapNode = Nothing

            Do
              s = sr.ReadLine()

              If Not s Is Nothing Then
                ' Build the various SiteMapNode objects and add
                ' them to the ArrayList collections. The format used
                ' is: URL,TITLE,DESCRIPTION,PARENTURL
                nodeValues = s.Split(","c)

                temp = New SiteMapNode(Me, _
                    HttpRuntime.AppDomainAppVirtualPath & "/" & nodeValues(0), _
                    HttpRuntime.AppDomainAppVirtualPath & "/" & nodeValues(0), _
                    nodeValues(1), _
                    nodeValues(2))

                ' Is this a root node yet?
                If aRootNode Is Nothing AndAlso _
                  (nodeValues(3) Is Nothing OrElse _
                   nodeValues(3) = String.Empty) Then
                  aRootNode = temp

                  ' If not the root node, add the node to the various collections.
                Else

                  siteMapNodes.Add(New DictionaryEntry(temp.Url, temp))

                  ' The parent node has already been added to the collection.
                  Dim parentNode As SiteMapNode = _
                      FindSiteMapNode(HttpRuntime.AppDomainAppVirtualPath & "/" & nodeValues(3))

                  If Not (parentNode Is Nothing) Then
                    childParentRelationship.Add(New DictionaryEntry(temp.Url, parentNode))
                  Else
                    Throw New Exception("Parent node not found for current node.")
                  End If
                End If
              End If
            Loop Until s Is Nothing
          Finally
            sr.Close()
          End Try
        Else
          Throw New Exception("File not found")
        End If
      End If
    End SyncLock
    Return
  End Sub
End Class