ImageList

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 _0078 {
 public partial class Form1 : Form {
  //номер изображения
  int number = 0;
  //индекс изображения
  int index = 0;
  public Form1() {
   InitializeComponent();
   pictureBox1.Image = imageList1.Images[0];
   label1.Text = "1";
  }
  //кнопка Left
  private void buttonLeft_Click(object sender, EventArgs e) {
   index--;
   if(index < 0) {
    index = imageList1.Images.Count-1;
   }
   pictureBox1.Image = imageList1.Images[index];
 
   number = index;
   label1.Text = (++number).ToString();
  }
  //кнопка Right
  private void buttonRight_Click(object sender, EventArgs e) {
   index++;
   if(index >= imageList1.Images.Count) {
    index = 0;
   }
   pictureBox1.Image = imageList1.Images[index];
   number = index;
   label1.Text = (++number).ToString();
  }
 }
}