C# ViewList

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Programiranje_domaci_3 {
    public partial class Form1 : Form {
        List<Knjiga> listKnjiga = new List<Knjiga>();

        public Form1() {
            InitializeComponent();
        }

        private void popuni() {
            Knjiga k = new Knjiga();

            k.Naziv = textBox1.Text;
            k.ImeAutora = textBox2.Text;
            k.Izdavac = comboBox1.SelectedItem.ToString();
            k.GodIzd = textBox3.Text;
            listKnjiga.Add(k);
        }
        private void button1_Click(object sender, EventArgs e) {
            popuni();
            textBox1.Clear();
            textBox2.Clear();
            comboBox1.SelectedIndex = -1;
            textBox3.Clear();
            textBox1.Focus();
        }

        private void button2_Click(object sender, EventArgs e) {
            if(!listView1.Visible) {
                foreach(Knjiga k in listKnjiga) {
                    string[] s = new string[] { k.Naziv, k.ImeAutora, k.Izdavac, k.GodIzd };
                    ListViewItem red = new ListViewItem(s);
                    red.Tag = k;
                    listView1.Items.Add(red);
                }
                listView1.Visible = true;
            }
            else
                listView1.Visible = false;
        }
    }
}