Client / Server question

HI all,

I'm fairly new at this, so bear with me if I am not coming across correctly.

I have an existing client/server applictaion.
On client side, I am selecting records from a datagrid.
The gridline(s) that are selected, are processed, and some columns end up in a custom type: GridLineItems
This class resides on the Client side (is this correct?)

This type has some properties :
-      FileLine as string
-      FileNaam as string
-      VerstuurCode as string
and so on

I use an arraylist to store my GridLineItems.
'declarations :
                  Dim arrline As GridLineItems
            Lines = New ArrayList

' Button Event:
For x = 0 To nbrRows - 1
                currID = Convert.ToString(grdSendFromFile.Item(tel, 0))
                Dim newID As String = Format_ID(currID)
                Dim soort As String = Convert.ToString(grdSendFromFile.Item(tel, 6))
                Dim verstuurCode As String = Convert.ToString(grdSendFromFile.Item(tel, 8))
                Dim verzendDatum As String = Convert.ToString(grdSendFromFile.Item(tel, 10))

                arrline = New GridLineItems
                arrline.FileLine = PrePareLine(newID, soort, verstuurCode)
                arrline.FileNaam = newID
                arrline.VerstuurCode = verstuurCode
                arrline.VerzendDatum = verzendDatum
                arrline.Soort = soort
                Lines.Add(arrline)
            Next

So far, so good.I now have an arraylist of GridLineItems objects.

The (for me) tricky part is to 'send' my ArrayList (Lines) to the serverside.
           
                  CallToServer = ApplicationContext.WsDMFATool.testme(Lines)

-------SERVER SIDE-------

Public Function testme(ByVal arr As ArrayList) As Boolean

            Dim returnValue As Boolean = Nothing
            Dim arrline As GridLineItems
            Dim tw As StreamWriter
            Try
                        For Each arrline In Lines
                              currID =
                              tw.WriteLine(arrline.FileLine) ' create textfile
                        Next

                Return True
            Catch ex As Exception

            End Try

        End Function

---------------------------

But of course, the type GridLineItems is unknown on Server Side

How do I get this to work?
Am I doing something fundamentally wrong?
Am I not declaring something I should?

Any help is appreciated.