Como restar dos listbox

Te recomiendo que para lo que entendí, debería utilizar otro control en vez del listbox, uno que te permita utilizar un arreglo de POR por Y dimensiones. Por lo menos un datagriview. De todas maneras ya he realizado el código para que te sirva con los listbox pero no se ve muy bien.
Sobre las tablas con las mismas columnas no es una BUENA PRACTICA, pero si quieres nos sentamos y vemos la película completa.
Imports System. Data
Imports
System. Data. SqlClient
Partial
Class ListBoxResta
Inherits System.Web.UI.Page
Public connex As New SqlConnection
Public Ds As New DataSet
Public dtVales As New DataTable
Public dtContraVales As New DataTable
Public dtResultado As New DataTable
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
connex.ConnectionString =
"Data Source=P5630;Initial Catalog=Northwind;Persist Security Info=True;User ID=sa;Password=sa"
If Not IsPostBack Then
Dim cadenaVales As String = "Select codigo , Nombre +' ' + cast(cantidad as varchar(18)),cantidad from Vales"
Dim cadenaRV As String = "Select codigo , Nombre +' ' + cast(cantidad as varchar(18)) ,cantidad from ContraVales"
' Dim cadenaVales As String = "Select codigo , Nombre ,cantidad from Vales"
' Dim cadenaRV As String = "Select codigo , Nombre ,cantidad from ContraVales"
LlenarListBox(ListBox1, dtVales, cadenaVales)
LlenarListBox(ListBox2, dtContraVales, cadenaRV)
ViewState(
"dtvales") = dtVales
ViewState(
"dtContraVales") = dtContraVales
Else
dtVales = ViewState(
"dtvales")
dtContraVales = ViewState(
"dtContraVales")
End If
End Sub
Public Sub LlenarListBox(byref lstbox as ListBox,byref dt as DataTable,sql as string )
Try
connex.Open()
Dim sqlda As New SqlDataAdapter
sqlda.SelectCommand =
New SqlCommand
sqlda.SelectCommand.Connection = connex
sqlda.SelectCommand.CommandText = sql
sqlda.Fill(dt)
If dt.Rows.Count > 0 Then
lstbox.DataTextField = dt.Columns.Item(1).ColumnName
lstbox.DataValueField = dt.Columns.Item(0).ColumnName
lstbox.DataSource = dt
Else
lstbox.DataSource =
Nothing
End If
lstbox.DataBind()
Catch ex As Exception
Throw ex
Finally
connex.Close()
End Try
End Sub
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
dtResultado = dtVales.Copy
Dim i As Integer
Dim drresult As DataRow
For Each rowVales As DataRow In dtVales.Rows
For Each rowContraVales As DataRow In dtContraVales.Rows
If rowVales(0).Equals(rowContraVales(0)) Then
drresult = dtResultado.Rows(i)
drresult(0) = rowVales(0)
drresult(1) = rowVales(1)
drresult(1) = rowVales(1) &" --> " & rowVales(2) - rowContraVales(2)
End If
Next
i = i + 1
Next
Me.ListBox3.DataTextField = dtResultado.Columns.Item(1).ColumnName
ListBox3.DataValueField = dtResultado.Columns.Item(0).ColumnName
ListBox3.DataSource = dtResultado
ListBox3.DataBind()
Catch ex As Exception
Throw ex
Finally
End Try
End Sub
End
Class