Adding data in dropdownlist

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Dropdownlist_Insertshow._Default" %>





   


   

   

       
       
                    ControlToValidate="txt_name" ErrorMessage="Please insert name">
       

                    Width="100px" />

   
       

       
   

   

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
namespace Dropdownlist_Insertshow
{
    public partial class _Default : System.Web.UI.Page
    {
        string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        string str;
        SqlCommand com;

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                dropbind();
            }
        }

        protected void btn_add_Click(object sender, EventArgs e)
        {
            DropDownList1.Items.Clear();
            SqlConnection con = new SqlConnection(strConnString);
            com = new SqlCommand();
            com.Connection = con;
            com.CommandType = CommandType.Text;
            com.CommandText = "insert into employee(name)values(@name)";
            com.Parameters.Clear();
            com.Parameters.AddWithValue("@name", txt_name.Text);
            if (con.State == ConnectionState.Closed)
                con.Open();
            com.ExecuteNonQuery();
            con.Close();
            Response.Write("Records successfully inserted");
            clear();
            dropbind();
        }
        private void clear()
        {
            txt_name.Text = "";
        }
        private void dropbind()
        {
           
            SqlConnection con = new SqlConnection(strConnString);
            DropDownList1.Items.Add("Choose Name");
            con.Open();
            str = "select * from  employee";
            com = new SqlCommand(str, con);
            SqlDataReader reader = com.ExecuteReader();
            while (reader.Read())
            {
            DropDownList1.Items.Add(reader["name"].ToString());
            }
            reader.Close();
            con.Close();
            }
       
    }
}