Modifying web.config programatically (SharePoint2010)

Here i'm going to add 2 web.config entries through code first i'm taking the backup copy of the original web.config and i'm adding the new entries.
Code shown below...

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Administration;
using System.Web.Administration;
using System.Configuration;
using System.Web;
using System.Web.Configuration;
using System.Reflection;
using System.Xml;
using System.Xml.Xsl;
using System.Xml.Serialization;
using System.Xml.XPath;

namespace ConsoleApplicationWebConfigBackUp
{
    class Program
    {
        static void Main(string[] args)
        {
            ApplyWebConfigModifications("http://localhost:5050");
//Taking the backup of the web.config file
            string physicalPath = oSite.WebApplication.IisSettings[SPUrlZone.Default].Path.ToString();
            File.Copy(physicalPath + @"\web.config", physicalPath + @"\web.config_backup_" + DateTime.Now.ToString("dd_mm_yyyy_hh_mm_ss") + ".config");
            Console.Read();
        }

        private static SPWebService contentService = null;
        private static SPWebApplication webApplication = null;

        public static bool ApplyWebConfigModifications(string webAppUri)
        {
             try
            {
                webApplication.WebConfigModifications.Clear();
                //Adding the RuntimeFilter element in the web.config 
                SPWebConfigModification spWebConfigModification = null;
                webApplication.WebConfigModifications.Remove(spWebConfigModification);
                spWebConfigModification = new SPWebConfigModification();
                spWebConfigModification.Owner = "UserName";
                spWebConfigModification.Path = "configuration/SharePoint";
                spWebConfigModification.Name = "RuntimeFilter[@Assembly='AssemblyName, Version=1.0.0.0, Culture=neutral, PublicKeyToken=2a73b4939c24f7ff']";
                spWebConfigModification.Value = "<RuntimeFilter Assembly='
AssemblyName, Version=1.0.0.0, Culture=neutral, PublicKeyToken=2a73b4939c24f7ff' Class='ClassName' BuilderURL='audience_chooser.aspx'/>";
spWebConfigModification.Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode;                 spWebConfigModification.Sequence = 0;                 webApplication.WebConfigModifications.Add(spWebConfigModification);                 webApplication.Update();                 contentService.ApplyWebConfigModifications();

                //anonymousIdentification
                spWebConfigModification = new SPWebConfigModification();
                spWebConfigModification.Owner = "UserName";
                spWebConfigModification.Path = "configuration/system.web";
                spWebConfigModification.Name = "anonymousIdentification";
                spWebConfigModification.Value = "<anonymousIdentification enabled='true'/>";
                spWebConfigModification.Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode;
                spWebConfigModification.Sequence = 0;
                webApplication.WebConfigModifications.Add(spWebConfigModification);
                webApplication.Update();
                contentService.ApplyWebConfigModifications();
                webApplication.Update();
                contentService.ApplyWebConfigModifications();

            }
            catch
            {
                throw;
            }
        }
    }
}