simple image upload to database and retrive

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 fileupld
{
    public partial class _Default : System.Web.UI.Page
    {
     
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["mycon"].ConnectionString);
        protected void Page_Load(object sender, EventArgs e)
        {
           
        }

      

        protected void onbtnupldclick(object sender, EventArgs e)
        {
            if (FileUpload1.HasFile)
            {

                string fileExtension = System.IO.Path.GetExtension(FileUpload1.FileName);

                if (fileExtension.ToLower() != ".jpg" && fileExtension.ToUpper() != ".jpeg")
                {
                    Response.Write("<script>alert('Please Upload .jpeg Or .jpg Files only');</script>");

                }
                else
                {

                    int fileSize = FileUpload1.PostedFile.ContentLength;

                    if (fileSize >= 1000000)
                    {
                        Response.Write("<script>alert('Please Upload less of 1 mb');</script>");
                    }
                    else
                    {
                        con.Open();
                        FileUpload1.SaveAs(Server.MapPath("~/folder/" + FileUpload1.FileName));
                        String s1 = FileUpload1.FileName;
                        String s2 = "insert into fileupload values('" + s1 + "')";
                        SqlCommand cmd = new SqlCommand(s2, con);
                        cmd.ExecuteNonQuery();
                        Response.Write("<script>alert('File Uploaded');</script>");
                    }
                }
            }
            else
            {

                Response.Write("<script>alert('Please Select The File');</script>");
            } 
        }

        protected void btnviewclick(object sender, EventArgs e)
        {
            con.Open();
            string sql = "select filename from fileupload";
            SqlCommand cmd = new SqlCommand(sql, con);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            da.Fill(dt);
            if (dt.Rows.Count > 0)
            {

                //string filePath = "Images\\" + dt.Rows[0][1].ToString(); 
                //Response.ContentType = "Images/jpg";
                //Response.AddHeader("Content-Disposition", "attachment;filename=\"" + filePath + "\"");
                //Response.TransmitFile(Server.MapPath(filePath));
                //Response.End();  
               
                //Response.AppendHeader("Content-Disposition", "attachment; filename=~/folder/"+ dt.Rows[0][0].ToString());
                
                Response.Write("<script>window.open('../Picture/"+dt.Rows[0][0].ToString()+"','-blank');</script>");
              
                
               
            }

           
                
            
        }
    }
}