Optimistic Data Concurrency

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Collections.Generic;
using System.Text;


public partial class _Default : System.Web.UI.Page 
{
    
      string strCheckupdated;
              string strupdated;

                    
     SqlConnection myConnection = new SqlConnection("server=10.10.10.57; uid=sa; password=12Test12; database=Northwind");

    
    protected void Button1_Click(object sender, EventArgs e)
    {
        myConnection.Open();
        SqlCommand myCommand = new SqlCommand("Select UpdateAt from student where sno='" + TextBox3.Text + "'", myConnection);
                    
        byte[] b = new byte[100];
        b = (Byte[]) myCommand.ExecuteScalar();
        
        strCheckupdated = System.Text.ASCIIEncoding.ASCII.GetString(b);
            
                   
                 
            
            if (string.Compare(Session["tempString"].ToString(), strCheckupdated) == 0)
            {
                myCommand = new SqlCommand("Update student set name='" + TextBox1.Text+ "',address='" + TextBox2.Text+ "' where sno ='" + TextBox3.Text +"'", myConnection);

                try
                {
                    myCommand.ExecuteNonQuery();
                    Response.Write("<script> alert('Record Updated Successfully') </script>");
                }
                catch (Exception)
                {
                Response.Write("<script> alert('Error During Updation')</script>");
                }
                
                TextBox3.Text="";
                TextBox1.Text="";
                TextBox2.Text = "";
                                
            }

            else
            {
                Response.Write("<script> alert('Record Updated by another User')</script>");
                TextBox3.Text = "";
                TextBox1.Text = "";
                TextBox2.Text = "";
                
                            }
                            Session.RemoveAll();
                        myConnection.Close();
        }
    
           
    protected void Button2_Click(object sender, EventArgs e)
    {
        Session.RemoveAll();
        string comstr = "SELECT name,address,UpdateAt FROM student where sno='"+ TextBox3.Text +"'";

        SqlCommand myCommand = new SqlCommand(comstr, myConnection);

        SqlDataReader reader = null;
        myConnection.Open();
        reader = myCommand.ExecuteReader();
        while (reader.Read())
        {
            TextBox1.Text = reader["name"].ToString();
            TextBox2.Text = reader["address"].ToString();

            byte[] b = new byte[100];
            b = (Byte[])reader["UpdateAt"];


            strupdated = System.Text.ASCIIEncoding.ASCII.GetString(b);
            
                
        }
        reader.Close();
        myConnection.Close();
  

        Session["tempString"] = strupdated;
        

    }
}