Form1.cs

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;
using System.IO;

namespace ZOO
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void mmuEnd_Click(object sender, EventArgs e)
        {
            Close();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            lblTime.Text = string.Format("Bây giờ là {0}:{1}:{2} ngày {3} tháng {4} năm {5}",
                                            DateTime.Now.Hour,
                                            DateTime.Now.Minute,
                                            DateTime.Now.Second,
                                            DateTime.Now.Day,
                                            DateTime.Now.Month,
                                            DateTime.Now.Year);
        }

        private void mmuLoad_Click(object sender, EventArgs e)
        {
            StreamReader reader = new StreamReader("Thumoi.txt");
            if (reader == null) return;
            string input = null;
            while ((input = reader.ReadLine()) != null)
            {
                lstThumoi.Items.Add (input);
            }
            reader.Close();
            using (StreamReader rs = new StreamReader("Danhsachthu.txt"))
            {
                input = null;
                while ((input = rs.ReadLine()) != null)
                    lstDanhsachthu.Items.Add(input);
            }

        }
        private void Save(object sender, EventArgs e)
        {
            StreamWriter writer = new StreamWriter("Danhsachthu.txt");
            if (writer == null) return;
            foreach(var item in lstDanhsachthu.Items)
            {
                writer.WriteLine(item.ToString());
            }
            writer.Close();
        }
        private void ListBox_MouseDown(Object sender, MouseEventArgs e)
        {
            ListBox lb = (ListBox)sender;
            int index = lb.IndexFromPoint(e.X, e.Y);
            lb.DoDragDrop(lb.Items[index].ToString(), DragDropEffects.Copy);
        }
        private void ListBox_DragEnter(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.Text))
                e.Effect = DragDropEffects.Copy;
            else
                e.Effect = DragDropEffects.Move;
        }
        private void lstDanhsachthu_DragDrop(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.Text))
            {
                ListBox lb = (ListBox)sender;
                lb.Items.Add(e.Data.GetData(DataFormats.Text));
            }
        }

        private void lstThumoi_DragDrop (object sender, DragEventArgs e)
        {
            if(e.Data.GetDataPresent(DataFormats.Text))
            {
                ListBox lb = (ListBox)sender;
                lb.Items.Add(e.Data.GetData(DataFormats.Text));
            }
        }
    }
}