File encryption using c#.net

try

            {

                string InputFile = Application.StartupPath + "\\softtechsolving.xls";   // this is excel file, i.e I  wanna to encrypt

                string OutputFile = = Application.StartupPath + "\\encrptsofttechsolving.xml";   // encrptsofttechsolving is file name after encryption file name                                                                                                saved that name  

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

                UnicodeEncoding UE = new UnicodeEncoding();

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

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

                RijndaelManaged RMCrypto = new RijndaelManaged();

                CryptoStream cs = new CryptoStream(fsCrypt,

                    RMCrypto.CreateEncryptor(key, key),

                    CryptoStreamMode.Write);

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

                int data;

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

                    cs.WriteByte((byte)data);

                fsIn.Close();

                cs.Close();

                fsCrypt.Close();

                MessageBox.Show("Backup Done", "Demo Software");

            }

            catch

            {

                MessageBox.Show("Encryption failed!", "Error");

            }

Namespace:

Adding

using System.Xml;

using System.IO;

using System.Security.Cryptography;

using System.Xml.Linq;

using System.Xml.Serialization;

using System.Data.SqlClient;