[عبد الرحمن]

جرب الكود هذا

Private fil As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) & "\" & "emad.txt"

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
If IO.File.Exists(fil) Then TextBox1.Text = IO.File.ReadAllText(fil)

End Sub

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

Private Sub TextBox2_TextChanged(sender As System.Object, e As System.EventArgs) Handles TextBox1.TextChanged
If Me.CheckBox1.Checked Then save()
End Sub

Sub save()
IO.File.WriteAllText(fil, TextBox1.Text)
End Sub