[Xx] Local Chat System

Public Class Form1
    Dim Sentmessage As String
    Dim User As String

    Private Sub Button1_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles Button1.Click
        If Button3.Text = "Login" Then
            MsgBox("You have to be logged in to chat!")
        Else
            User = TextBox3.Text
            Sentmessage = TextBox2.Text
            ListBox1.Items.Add(User + ": " + Sentmessage)
            TextBox2.Clear()
        End If
    End Sub

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

        If My.Computer.FileSystem.FileExists(".\Usernames\" + TextBox3.Text + ".txt") Then
            MsgBox("The Username " + TextBox3.Text + ", is already in use! Please choose another one!")
        Else
            My.Computer.FileSystem.CreateDirectory(".\Usernames\")
            My.Computer.FileSystem.WriteAllText(".\Usernames\" + TextBox3.Text + ".txt", TextBox3.Text, True)
            My.Computer.FileSystem.CreateDirectory(".\Passwords\")
            My.Computer.FileSystem.WriteAllText(".\Passwords\" + TextBox3.Text + ".txt", TextBox4.Text, True)
        End If

    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        If My.Computer.FileSystem.FileExists(".\Usernames\" + TextBox3.Text + ".txt") Then
            If My.Computer.FileSystem.ReadAllText(".\Passwords\" + TextBox3.Text + ".txt").Equals(TextBox4.Text) Then
                If Button3.Text = "Log Out" Then
                    TextBox3.ReadOnly = False
                    TextBox4.ReadOnly = False
                    TextBox3.Clear()
                    TextBox4.Clear()
                    Button2.Visible = True
                    Button3.Text = "Login"
                    MsgBox("Welcome back later!")
                Else
                    TextBox3.ReadOnly = True
                    TextBox4.ReadOnly = True
                    Button3.Text = "Log Out"
                    Button2.Visible = False
                    MsgBox("You are now logged in Mr " + TextBox3.Text + "!")
                End If
            End If
            Else
                MsgBox("The username or Password is incorrect, please try again!")
            End If
    End Sub
End Class