File decryption using c#.net

c# code:          

  string InputFile = Application.StartupPath +"\\ encrptsofttechsolving.xml ";   // this is excel file, i.e I  wanna to deencrypt

                string OutputFile = = Application.StartupPath +"\\softtechsolving.xls ";   // softtechsolving is file name after decryption of  encrptsofttechsolving.xml

            XmlDocument XDoc1 = new XmlDocument();

            try

            {

                string password = @"xxxxxxx"; // Your Key Here

                UnicodeEncoding UE = new UnicodeEncoding();

                byte[] key = UE.GetBytes(password);

                FileStream fsCrypt = new FileStream(inputFile, FileMode.Open);

                RijndaelManaged RMCrypto = new RijndaelManaged();

                CryptoStream cs = new CryptoStream(fsCrypt,

                    RMCrypto.CreateDecryptor(key, key),

                    CryptoStreamMode.Read);

                FileStream fsOut = new FileStream(outputFile, FileMode.Create);

                int data;

                while ((data = cs.ReadByte()) != -1)

                    fsOut.WriteByte((byte)data);

                fsOut.Close();

                cs.Close();

                fsCrypt.Close();

            }

            catch (Exception ex)

            {

                //MessageBox.Show("DecryptFile failed!", "Error");

            }Namespace:

Adding

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.IO;

using System.Security.Cryptography;

using System.Xml;