unauthorized access exception was handled by user code error solution

using System;
using System.IO;
using System.Collections;
using System.Data;
using System.Configuration;
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.Sql;
using System.Data.SqlClient;
using iTextSharp.text;
using iTextSharp.text.pdf;

public partial class donorcard : System.Web.UI.Page
{
    SqlConnection cn;
    SqlCommand cmd;
    protected void Page_Load(object sender, EventArgs e)
    {
        cn = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=E:\\organ2\\App_Data\\Database.mdf;Integrated Security=True;User Instance=True");
        cn.Open();
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        string donorid = TextBox1.Text;
        string donorname = TextBox5.Text;
        string address = TextBox2.Text;
        string anypart = RadioButtonList1.Text;
        string wish = CheckBoxList2.Text;
        string witnessname = TextBox3.Text;
        string witnessphno = TextBox4.Text;
        string name = FileUpload1.FileName;
        FileUpload1.SaveAs(Server.MapPath("~/images/" + name));
        string photo = "~/images/" + name;
        cmd = new SqlCommand("insert into donorcard values('" + donorid + "','" + donorname + "','" + address + "','" + anypart + "','" + wish + "','" + witnessname + "','" + witnessphno + "','" + photo + "')", cn);
        cmd.ExecuteNonQuery();
        TextBox1.Text = "";
        TextBox2.Text = "";
        TextBox3.Text = "";
        TextBox4.Text = "";
        TextBox5.Text = "";
        RadioButtonList1.Text = "";
        CheckBoxList2.Text = "";
        //Response.Redirect("~/donor mainpage.aspx");00
        //Response.ContentType = "Application/pdf";
        //Response.AppendHeader("Content-Disposition", "attachment;filename=Test_PDF.pdf");
        //Response.TransmitFile(Server.MapPath("~//pdf.pdf"));
        //Response.End();
        Document doc = new Document(iTextSharp.text.PageSize.LETTER, 10, 10, 42, 35);
        PdfWriter wri = PdfWriter.GetInstance(doc, new FileStream("Donorcard.pdf", FileMode.Create));
        doc.Open();
        Paragraph paragraph = new Paragraph("This is your Donorcard.Get signature form the witness and keep it safe.");
        doc.Add(paragraph);
        doc.Close();
    }

}