Sub WriteListViewToCSVFile() 
Dim CSVWriter As New StreamWriter("C:\Test.csv") 
For i As Integer = 0 To Main.ListView1.Items.Count - 1 
For j As Integer = 0 To Main.ListView1.Columns.Count - 1 
CSVWriter.Write(Main.ListView1.Items(i).SubItems(j).Text) 
Next 
CSVWriter.WriteLine() 
Next 
CSVWriter.Close() 
End Sub 

Main Form Code 

'Add a button to your form and call the new subroutine when the button is pressed. 

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 
WriteListViewToCSVFile() 
End Sub