decrypt naar/in de zelfde file

[infur]

ik heb een code die encrypt en decrypt maar hij doet het naar een andere file nu wil ik het in de zelfde file hebben maar het lukt mij niet wil iemand me helpen bedankt.

Private Sub Button7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button7.Click
        Try

            Dim myDESProvider As DESCryptoServiceProvider = New DESCryptoServiceProvider()

            myDESProvider.Key = ASCIIEncoding.ASCII.GetBytes("12345678")
            myDESProvider.IV = ASCIIEncoding.ASCII.GetBytes("12345678")

            Dim myICryptoTransform As ICryptoTransform = myDESProvider.CreateEncryptor(myDESProvider.Key, myDESProvider.IV)

            Dim ProcessFileStream As FileStream = New FileStream(My.Application.Info.DirectoryPath + "\saves\slot1.txt", FileMode.Open, FileAccess.Read)
            Dim ResultFileStream As FileStream = New FileStream(My.Application.Info.DirectoryPath + "\saves\slot1des.txt", FileMode.Create, FileAccess.Write)
            Dim myCryptoStream As CryptoStream = New CryptoStream(ResultFileStream, myICryptoTransform, CryptoStreamMode.Write)

            Dim bytearrayinput(ProcessFileStream.Length - 1) As Byte

            ProcessFileStream.Read(bytearrayinput, 0, bytearrayinput.Length)
            myCryptoStream.Write(bytearrayinput, 0, bytearrayinput.Length)

            myCryptoStream.Close()
            ProcessFileStream.Close()
            ResultFileStream.Close()

        Catch ex As Exception
            Console.WriteLine(ex.Message)

        End Try
    End Sub

   


 Private Sub Button8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button8.Click
        Try
            Dim myDESProvider As DESCryptoServiceProvider = New DESCryptoServiceProvider()

            myDESProvider.Key = ASCIIEncoding.ASCII.GetBytes("12345678")
            myDESProvider.IV = ASCIIEncoding.ASCII.GetBytes("12345678")

            Dim DecryptedFile As FileStream = New FileStream(My.Application.Info.DirectoryPath + "\saves\slot1des.txt", FileMode.Open, FileAccess.Read)
            Dim myICryptoTransform As ICryptoTransform = myDESProvider.CreateDecryptor(myDESProvider.Key, myDESProvider.IV)
            Dim myCryptoStream As CryptoStream = New CryptoStream(DecryptedFile, myICryptoTransform, CryptoStreamMode.Read)

            Dim myDecStreamReader As New StreamReader(myCryptoStream)
            Dim myDecStreamWriter As New StreamWriter(My.Application.Info.DirectoryPath + "\saves\slot1des.txt")
           
            myDecStreamWriter.Write(myDecStreamReader.ReadToEnd())


            myCryptoStream.Close()
            myDecStreamReader.Close()
            myDecStreamWriter.Close()
        Catch ex As Exception

            Console.WriteLine(ex.ToString())
        End Try
    End Sub