'读取方法一：

Imports System.IO
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Me.ListBox1.Items.Clear()
        Dim StrRed As StreamReader = New StreamReader("D:\111.txt", System.Text.Encoding.Default)

        While Not StrRed.EndOfStream
            Me.ListBox1.Items.Add(StrRed.ReadLine())
        End While
        StrRed.Dispose()

    End Sub
End Class

'读写方法二：

写入：

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim strR As New StreamWriter("D:\111.txt", True)'参数True表示 在原来的数据上面添加，如果为False这删除原来的数据 重新写入数据
        strR.WriteLine(Me.TextBox2.Text)
        strR.Dispose()
End Sub

读取：

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim strR As New StreamReader("D:\111.txt")

        While Not strR.EndOfStream
            Me.TextBox1.Text += strR.ReadLine() & vbCrLf
        End While
        strR.Dispose()
End Sub