Issue with DES encryption

static void EncryptFile(string sInputFilename, string sOutputFilename, string sKey)
        {
            {
                SqlConnection conn = null;
                SqlDataReader rdr = null;
                try
                {
                    conn = new
                    SqlConnection(ConfigurationManager.ConnectionStrings["mycon"].ConnectionString);
                    SqlCommand cmd = new SqlCommand("my_proc", conn);
                    cmd.CommandType = CommandType.StoredProcedure;
                    conn.Open();
                    SqlDataReader sqlReader = cmd.ExecuteReader();
                    string suffix = null;
                    string pKey = null;
                    Object xsuffix = new Object();
                    Object ypKey = new Object();
                    while (sqlReader.Read())
                    {
                        ypKey = sqlReader.IsDBNull(sqlReader.GetOrdinal("PrimaryNum"))
                            ? String.Empty
                            : sqlReader.GetValue(sqlReader.GetOrdinal("PrimaryNum"));
                        xsuffix = sqlReader.IsDBNull(sqlReader.GetOrdinal("Suffix"))
                            ? String.Empty
                            : sqlReader.GetValue(sqlReader.GetOrdinal("Suffix"));
                        suffix = xsuffix.ToString();
                        pKey = ypKey.ToString();
                    }
                    sqlReader.Close();
                    byte[] salt = Encoding.ASCII.GetBytes(suffix);
                    FileStream fsInput = new FileStream(sInputFilename,
                          FileMode.Open,
                          FileAccess.Read);
                    byte[] bytearrayinput = new byte[fsInput.Length];
                    fsInput.Read(bytearrayinput, 0, bytearrayinput.Length);
                    fsInput.Close();
                    FileStream fsEncrypted = new FileStream(sOutputFilename,
                       FileMode.Create,
                       FileAccess.Write);
                    DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
                    Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(pKey, salt);
                    DES.Key = deriveBytes.GetBytes(8);
                    DES.Mode = CipherMode.ECB;
                    DES.Padding = PaddingMode.PKCS7;
                    ICryptoTransform desencrypt = DES.CreateEncryptor();
                    CryptoStream cryptostream = new CryptoStream(fsEncrypted,
                       desencrypt,
                       CryptoStreamMode.Write);

                    cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);
                    cryptostream.FlushFinalBlock();
                    cryptostream.Close();
                    fsEncrypted.Close();
                }
                finally
                {
                    if (conn != null)
                    {
                        conn.Close();
                    }
                    if (rdr != null)
                    {
                        rdr.Close();
                    }
                }
            }
        }
What could be wrong? i tried different padding mode already. No luck :(