duplicate record is created in database on page reload

Question

How to Prevent or Avoid Duplicate Record Insertion on Refresh(F5) Click in Browser in ASP.Net ?

 

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;

namespace Student_Management
{
    public partial class Student_Registration : System.Web.UI.Page
    {
        SqlConnection con = new SqlConnection(@"Data Source=192.168.31.222;Initial Catalog=Student_Database;Integrated Security=True;MultipleActiveResultSets=true;");

        protected void Page_Load(object sender, EventArgs e)
        {
            if (con.State == ConnectionState.Open)
            {
                con.Close();
               // Response.Redirect(Request.Url.ToString(), false);
            }

            con.Open();

        }

        protected void Button2_Click(object sender, EventArgs e)
        {
            if (TextBox1.Text == String.Empty)
            {
                Label1.Text = "Fill Registration Number" ;
            }
            else if(TextBox2.Text == String.Empty)
            {
                Label1.Text = "Fill Name" ;
            }
            else if (TextBox3.Text == String.Empty)
            {
                Label1.Text = "Fill Qualification" ;
            }
            else if (TextBox4.Text == String.Empty)
            {
                Label1.Text = "Fill Location" ;
            }
            else if (TextBox5.Text == String.Empty)
            {
                Label1.Text = "Fill Phone";
            }
            else if (TextBox6.Text == String.Empty)
            {
                Label1.Text = "Fill Email ID";
            }
            else {
                SqlCommand cmd = con.CreateCommand();
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = "insert into Student_Details values('" + TextBox1.Text + "','" + TextBox2.Text + "','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','" + TextBox6.Text + "')";
                cmd.ExecuteNonQuery();
                TextBox1.Text = "";
                TextBox2.Text = "";
                TextBox3.Text = "";
                TextBox4.Text = "";
                TextBox5.Text = "";
                TextBox6.Text = "";
                Response.Write("<script>alert('INSERT NEW STUDENT DATA SUCCESS')</script>");

                Label1.Visible = false;

                con.Close();
            }



        }
    }
}