Virtual list views, also known as owner data, appear to the user as any other list view but the underlying code to populate them is optimized for large data sets. A virtual list-view control maintains very little item state information itself. List views that contain more than several hundred items generally achieve significant performance improvement as virtual lists.

The decision to use a virtual list view should be based on the cost of fetching the data as well as the volume of data. In the case of a remote database query with a huge result set a virtual list view would be an obvious choice.

When a ListView object is in virtual mode, it creates ListViewItem objects dynamically instead of using the Items collection. This event is raised when the object must create a ListViewItem object. A handler for this event should create the appropriate ListViewItem or retrieve it from the cache, and pass it back by way of the Item property.

The best example for Virtual List view is Windows Explorer. There might be thousands of files in a folder. All these file information will not be added at once. Mostly the explorer provides information only for the visible items.

When we implement a virtual list controls, we will not add the items to the list view. Instead, we will set only the number of elements in the listview. A callback will be issued by the control when it requires to display a specific item.

How to enable a Virtual Mode for List View?

listView1.VirtualMode = true;
listView1.RetrieveVirtualItem += new RetrieveVirtualItemEventHandler(listView1_RetrieveVirtualItem);

How to provide ListViewItem

You an see that we’ve added a event handler for retrieving the virtual items. Just implement the callback and provide the ListViewItem info.

void listView1_RetrieveVirtualItem(object sender, RetrieveVirtualItemEventArgs e)
{
    e.Item = new ListViewItem();
    e.Item.Text = bornInfo[e.ItemIndex].Title;
    e.Item.BackColor = Color.YellowGreen;
    e.Item.Font = new Font("Consolas", 11);
    e.Item.SubItems.Add( bornInfo[e.ItemIndex].Description);
}

How to set the number of items in the list view?

// Set the count
listView1.VirtualListSize = bornInfo.Count;

A complete sample to retrieve Born On This Day Info from IMDB

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

namespace VirtualListControlDemo
{

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            // Enable Virtual List mode
            listView1.VirtualMode = true;
            listView1.RetrieveVirtualItem += new RetrieveVirtualItemEventHandler(listView1_RetrieveVirtualItem);
            listView1.View = View.Details;
            listView1.Columns.Add("Person", 150 );
            listView1.Columns.Add("Description", 400);
        }

        // Draw the item
        void listView1_RetrieveVirtualItem(object sender, RetrieveVirtualItemEventArgs e)
        {
            e.Item = new ListViewItem();
            e.Item.Text = bornInfo[e.ItemIndex].Title;
            e.Item.BackColor = Color.YellowGreen;
            e.Item.Font = new Font("Consolas", 11);
            e.Item.SubItems.Add( bornInfo[e.ItemIndex].Description);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            // Load the XML document
            XDocument xmlDoc = XDocument.Load("http://rss.imdb.com/daily/born/");
            // Parse the required info
            bornInfo = (List<BornOnThisDay>)(from item in xmlDoc.Descendants("item")
                select new BornOnThisDay
                {
                    Title = item.Element( "title").Value,
                    Description = item.Element("description").Value
                }).ToList();

            // Set the count
            listView1.VirtualListSize = bornInfo.Count;
        }

        List<BornOnThisDay> bornInfo = new List<BornOnThisDay>();
    }
    public class BornOnThisDay
    {
        public string Title;
        public string Description;
    }
}