[RESOLVED] sum listbox items

[toecutter]

Iam adding a elemnet from a xml file into listbox

Option Strict On
Option Explicit On
Option Infer Off
Imports System.IO
Imports System.Xml
Imports System.Net
Imports System.Windows.Forms.VisualStyles.VisualStyleElement.ListView

Public Class Form1
    Dim path As String = ("F:\ESS_Contacts\dsContactsSUBS.xml")
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim ds As New DataSet
        ds.ReadXml(path)
        ListBox1.DataSource = ds.Tables("Contacts")
        ListBox1.DisplayMember = "amount"
    End Sub

    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Dim totall As Double
        For Each item As Double In ListBox1.Items
            totall += item
        Next
        txtTotalCost.Text = CType(totall, String)

    End Sub
End Class

I am then trying to sum the list but keeping getting errors

System.InvalidCastException: 'Conversion from type 'DataRowView' to type 'Double' is not valid.'

I have worked out its because of the way i add the data

Ive tried heaps of examples but always get the same error.

ps. ignore images, seems to be no way to delete once uploaded...