Imports System.IO 
Public Class Form1 
Private Sub btn_add_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn_add.Click 
If OpenFileDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then 
Dim S() As String = OpenFileDialog1.FileNames 'un array che contiene i nomi dei file scelti 
Dim File As String 
For Each File In S 
ListBox1.Items.Add(File) 
Next 
End If 
End Sub 

Private Sub btn_create_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn_create.Click 
If SaveFileDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then 
Dim W As New IO.StreamWriter(SaveFileDialog1.FileName) 
Dim R As IO.StreamReader 
Dim File As String 

'il valore massimo della proprietà value della progressbar 
ProgressBar1.Maximum = ListBox1.Items.Count 
'il valore iniziali della progressbar 
ProgressBar1.Value = 0 
LabelStatus.Text = "Creazione File in corso..." 

' scrittura del file 
For i As Int16 = 0 To ListBox1.Items.Count - 1 
File = ListBox1.Items(i) 
R = New IO.StreamReader(File) 
W.WriteLine(R.ReadToEnd) 
R.Close() 
R = Nothing 
ProgressBar1.Value += 1 
Next 
LabelStatus.Text = "File creato" 
ProgressBar1.Value = 0 
End If 
End Sub 
End Class