Как разобраться с программой! - Visual Basic .NET - Ответ 1558093

Public Class Form1
    Dim Key As Byte() = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16} 'Ключ
    Dim IV As Byte() = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16} 'Ключ
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Try
            Dim Users() As String = IO.Directory.GetFiles(Application.StartupPath, "*.u", IO.SearchOption.TopDirectoryOnly)
            For Each Us As String In Users
                If TextBox1.Text = IO.Path.GetFileNameWithoutExtension(Us) Then
                    MsgBox("Пользователь с таким логином уже зарегистрирован", MsgBoxStyle.Exclamation)
                    Exit Sub
                    Exit For
                End If
            Next
            If TextBox1.TextLength < 4 Then
                MsgBox("Имя пользователя должно состоять из 4 и более букв", MsgBoxStyle.Exclamation)
                Exit Sub
            End If
            If TextBox2.TextLength < 6 Then
                MsgBox("Пароль должен включать не менее 6 символов", MsgBoxStyle.Exclamation)
                Exit Sub
            End If
            Dim User As String = TextBox1.Text
            Dim Pass As String = TextBox2.Text
            Encrypt(".\" & TextBox1.Text & ".u", TextBox2.Text)
            MsgBox("Поздравляем, " & User & "! Вы успешно зарегистрированы!", MsgBoxStyle.Information)
        Catch ex As Exception
            MsgBox(ex.ToString, MsgBoxStyle.Critical)
        End Try
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        If TextBox1.Text = "" Or TextBox2.Text = "" Then
            MsgBox("Все поля обязательны для заполнения", MsgBoxStyle.Exclamation)
            Exit Sub
        End If
        Try
            Dim UE As New IO.FileInfo(".\" & TextBox1.Text & ".u")
            If UE.Exists = False Then
                MsgBox("Такой пользователь не зарегистрирован", MsgBoxStyle.Exclamation)
                Exit Sub
            End If
            If TextBox2.Text = Decrypt(".\" & TextBox1.Text & ".u") Then
                MsgBox("Добро пожаловать", MsgBoxStyle.Information)
            Else
                MsgBox("Неверный пароль!", MsgBoxStyle.Exclamation)
            End If
        Catch ex As Exception
            MsgBox(ex.ToString, MsgBoxStyle.Critical)
        End Try
    End Sub
 
    Private Sub Encrypt(ByVal fName As String, ByVal txtEncrypt As String)
        Dim RMCrypto As New Security.Cryptography.RijndaelManaged
        Dim fs As New IO.FileStream(fName, IO.FileMode.Create)
        Dim CryptStream As New Security.Cryptography.CryptoStream(fs, RMCrypto.CreateEncryptor(Key, IV), Security.Cryptography.CryptoStreamMode.Write)
        Dim SWriter As New IO.StreamWriter(CryptStream)
        SWriter.Write(txtEncrypt)
        SWriter.Close()
        fs.Close()
        CryptStream.Close()
    End Sub
    Private Function Decrypt(ByVal fName As String) As String
        Dim RMCrypto As New Security.Cryptography.RijndaelManaged
        Dim fs As New IO.FileStream(fName, IO.FileMode.Open)
        Dim CryptStream As New Security.Cryptography.CryptoStream(fs, RMCrypto.CreateDecryptor(Key, IV), Security.Cryptography.CryptoStreamMode.Read)
        Dim SReader As New IO.StreamReader(CryptStream)
        Decrypt = SReader.ReadToEnd()
        SReader.Close()
        fs.Close()
        CryptStream.Close()
    End Function
End Class