save to textfile and get values from textfile to a listbox (vb.net)

I'm not quite sure what you mean by saving a "textfile to listbox", but here's how you would save a textbox to a file:

Imports System.IO

Dim f as StreamWriter = New StreamWriter("C:\temp\file.txt")
f.Write(textBox1.Text)
f.Close()

i'm getting an error on Imports.
It says that statements must precede any declarations.
what does that mean?

Imports System.IO goes on the absolute first line above all other code. The rest of the code goes in your module.

It working.
But when i'm adding it delete the old value.
How will i do so it just adds the new value after the old?


About listbox:

I want to get that are in the text to the listbox.
So the listbox will get all the values that are  in the text file.