Imports System.IO
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If File.Exists("C:/TextFile.txt") Then
            Dim ioFile As New StreamReader("C:/TextFile.txt")
            Dim ioLine As String
            Dim ioLines As String
            ioLine = ioFile.ReadLine
            ioLines = ioLine
            While Not ioLine = ""
                ioLine = ioFile.ReadLine
                ioLines = ioLines & vbCrLf & ioLine
            End While
            TextBox1.Text = (ioLines)
            ioFile.Close()
        End If
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

        Dim ioFile As New StreamWriter("C:/TextFile.txt")
        ioFile.Write(TextBox1.Text)
        ioFile.Write(TextBox2.Text)
        ioFile.Write(vbNewLine
                     )
        ioFile.Write(TextBox3.Text)
        ioFile.Close()
    End Sub
End Class