VB.net Base64对文件进行加密与解密的问题?

 Public Function EncodeBase64(ByVal code As String) As String

        Dim encode As String = ""

        Dim bytes As Byte() = Encoding.Default.GetBytes(code)

        Try

            encode = Convert.ToBase64String(bytes)

        Catch

            encode = code

        End Try

        Return encode

    End Function





    Public Function DecodeBase64(ByVal code As String) As String

        Dim decode As String = ""

        Dim bytes As Byte() = Convert.FromBase64String(code)

        Try

            decode = Encoding.Default.GetString(bytes)

        Catch

            decode = code

        End Try

        Return decode

    End Function



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

            Dim xtms, xtxx, xtlx ，jsjm, yhm, cpu，cpuid, zbcs, zbid，ypcs, ypid, ip，mac, ncrl, xkcs ，xk, scsj As String

            xtms = EncodeBase64(Label14.Text)

            xtxx = EncodeBase64(TextBox1.Text)

            xtlx = EncodeBase64(TextBox2.Text)

            jsjm = EncodeBase64(TextBox3.Text)

            yhm = EncodeBase64(TextBox4.Text)

            cpu = EncodeBase64(TextBox5.Text)

            cpuid = EncodeBase64(TextBox6.Text)

            zbcs = EncodeBase64(TextBox7.Text)

            zbid = EncodeBase64(TextBox8.Text)

            ypcs = EncodeBase64(TextBox9.Text)

            ypid = EncodeBase64(TextBox10.Text)

            ip = EncodeBase64(TextBox11.Text)

            mac = EncodeBase64(TextBox12.Text)

            ncrl = EncodeBase64(TextBox13.Text)

            xkcs = EncodeBase64(TextBox14.Text)

            xk = EncodeBase64(TextBox15.Text)

            scsj = EncodeBase64(ToolStripStatusLabel2.Text)



            My.Computer.FileSystem.WriteAllText("data.ini", "[信息配置]" + vbCrLf + "系统模式：" + xtms + vbCrLf + "系统信息：" + xtxx + vbCrLf + "系统类型：" + xtlx + vbCrLf + "计算机名：" + jsjm + vbCrLf + "用户名：" + yhm + vbCrLf + "CPU：" + cpu + vbCrLf + "CPUID：" + cpuid + vbCrLf + "主板厂商：" + zbcs + vbCrLf + "主板序号：" + zbid + vbCrLf + "硬盘厂商：" + ypcs + vbCrLf + "硬盘序号：" + ypid + vbCrLf + "IP地址：" + ip + vbCrLf + "MAC地址：" + mac + vbCrLf + "内存容量：" + "MB" + ncrl + vbCrLf + "显卡厂商：" + xkcs + vbCrLf + "显卡：" + xk + vbCrLf + "生成时间：" + scsj, False)



            MsgBox("已记录")