Convert date format ddmmyy(251210) to yyyymmdd (20101225).

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;
namespace CodeProjectAnswer
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            DateTime d = DateTime.Now;
            string date = DateTime.Now.ToString("ddMMyy");
            txtDate.Text = date.ToString();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            string DayMonthYear="";
            string cdate = txtDate.Text.ToString();
            if (cdate.Length > 0)
            {
               string day=cdate.Substring(0, 2);
               string month = cdate.Substring(2, 2);
               string year = cdate.Substring(4, 2);
               if (DateTime.Now.ToString("yy") == year)
               {
                   DayMonthYear = DateTime.Now.ToString("yyyy");
                   if (DateTime.Now.ToString("MM") == month)
                   {
                       DayMonthYear += DateTime.Now.ToString("MM");
                       if (DateTime.Now.ToString("dd") == day)
                       {
                           DayMonthYear += DateTime.Now.ToString("dd");
                           txtConvertDate.Text = DayMonthYear.ToString();
                       }
                   }
               }
            }
        }
    }
}