List<Termek> osztaly = new List<Termek>();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                FillDropdown();

            }
        }
       private void FillDropdown(){
            FillOsztaly();
            DropDownList1.Items.Add("-Valassz gyartot-");
            DropDownList1.Items.AddRange(osztaly.Select(i => new ListItem(i.Gyarto)).Distinct().ToArray());

            DropDownList3.Items.Add("-Valassz processzort-");
            DropDownList3.Items.AddRange(osztaly.Select(i => new ListItem(i.Processzor)).Distinct().ToArray());

            DropDownList4.Items.Add("-Valassz kamerat-");
            DropDownList4.Items.AddRange(osztaly.Select(i => new ListItem(i.Kamera)).Distinct().ToArray());

            DropDownList5.Items.Add("-Valassz kijelzot-");
            DropDownList5.Items.AddRange(osztaly.Select(i => new ListItem(i.Kepernyo)).Distinct().ToArray());
    }

        protected void FillOsztaly() {
            string filename = Server.MapPath("~/webaruhaz1.txt");
            using (StreamReader reader = new StreamReader(filename))
            {
                string line;
                while ((line = reader.ReadLine())!=null) {
                    Termek termek = new Termek();
                    termek.Id = line.Substring(0, 6).Trim();
                    termek.Nev = line.Substring(6, 25);
                    termek.Gyarto = line.Substring(31, 20).Trim();
                    termek.Ram = line.Substring(31, 5).Trim();
                    termek.Processzor = line.Substring(56, 15).Trim();
                    termek.Kamera = line.Substring(71, 10).Trim();
                    termek.Kepernyo = line.Substring(81, 5).Trim();
                    termek.Kep = line.Substring(91, 30).Trim();
                    termek.Ar = line.Substring(121, 10).Trim();
                    osztaly.Add(termek);
                }
            }
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            FillOsztaly();
                List<Termek> eredmeny = osztaly;
            if (DropDownList1.SelectedIndex > 0) {
            eredmeny = eredmeny.FindAll(i=>i.Gyarto.Contains(DropDownList1.SelectedItem.Text));

            if (DropDownList2.SelectedIndex > 0)
            {
                eredmeny = eredmeny.FindAll(i => i.Ram.Contains(DropDownList2.SelectedItem.Text));

            }

            if (DropDownList3.SelectedIndex > 0)
            {
                eredmeny = eredmeny.FindAll(i => i.Processzor.Contains(DropDownList3.SelectedItem.Text));

            }

            if (DropDownList4.SelectedIndex > 0)
            {
                eredmeny = eredmeny.FindAll(i => i.Kamera.Contains(DropDownList4.SelectedItem.Text));

            }

            }
            if (DropDownList5.SelectedIndex > 0)
            {
                eredmeny = eredmeny.FindAll(i => i.Kepernyo.Contains(DropDownList5.SelectedItem.Text));

            }
            GridView1.DataSource = eredmeny;
            GridView1.DataBind();
        }
    }
}