Object reference not set to an instance of an object. Data not loading in dropdown

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                
            }
                if ( Request.QueryString.Count > 0)
                {
                    Loaddata();
                }
            }
        
        protected void Loaddata()
        {
            SqlConnection con = new SqlConnection("Data Source=jayraj-pc\\sqlexpress;Initial Catalog=Internship;Integrated Security=True;Pooling=False");

            
            SqlCommand cmd3 = new SqlCommand("select * from Internship where InternshipID=" + Convert.ToInt16(Request.QueryString["InternshipID"].ToString()), con);

            SqlDataAdapter daa = new SqlDataAdapter(cmd3);
            DataTable dtt = new DataTable();
            daa.Fill(dtt);
            if (dtt.Rows.Count > 0)
            {
                title.Text = dtt.Rows[0]["Title"].ToString();
                role.Text = dtt.Rows[0]["InternshipRole"].ToString();
                noofopenings.Text = dtt.Rows[0]["NoOfOpenings"].ToString();
                startdate.Text = dtt.Rows[0]["InternshipStartDate"].ToString();
                enddate.Text = dtt.Rows[0]["ApplicationDeadLine"].ToString();
                duration.Text = dtt.Rows[0]["Duration"].ToString();
                type.SelectedItem.Text = dtt.Rows[0]["Type"].ToString();
                DropDownList2.SelectedItem.Text = dtt.Rows[0]["InternshipCity"].ToString();
                DropDownList3.SelectedItem.Text = dtt.Rows[0]["Degree"].ToString();
               
                //Response.Write(dtt.Rows[0]["Degree"].ToString());
                DropDownList4.SelectedItem.Text = dtt.Rows[0]["Branch"].ToString();
                Response.Write(dtt.Rows[0]["Branch"].ToString());
                

                int_address.Text = dtt.Rows[0]["Address"].ToString();
                int_contactno.Text = dtt.Rows[0]["ContactNo"].ToString();
                
                RadioButtonList1.Items.FindByText(dtt.Rows[0]["Stipend"].ToString()).Selected = true;
                RadioButtonList2.Items.FindByText(dtt.Rows[0]["FullTimeJob"].ToString()).Selected = true;
                
                skills_req.Text = dtt.Rows[0]["SkillsRequired"].ToString();





            }
        }