using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; namespace VirtualMode { partial class VirtualModeForm : Form { private List<DataObject> m_Data = new List<DataObject>(); private List<bool> m_Visited = new List<bool>(); public VirtualModeForm() { InitializeComponent(); m_Grid.CellValueNeeded += OnCellValueNeeded; m_GetVisitedCountButton.Click += OnGetVisitedCount; InitData(); InitGrid(); } private void InitData() { for (int i = 0; i < 1000001; i++) { m_Visited.Add(false); DataObject obj = new DataObject(); obj.Id = i; obj.Val = 2 * i; m_Data.Add(obj); } } private void InitGrid() { m_Grid.VirtualMode = true; m_Grid.ReadOnly = true; m_Grid.AllowUserToAddRows = false; m_Grid.AllowUserToDeleteRows = false; m_Grid.ColumnCount = 3; m_Grid.Rows.Add(); m_Grid.Rows.AddCopies(0, 1000000); // Uncomment the next line and comment out the // the rest of the method to switch to data bound mode //m_Grid.DataSource = m_Data; } private void OnCellValueNeeded(object sender, DataGridViewCellValueEventArgs e) { m_Visited[e.RowIndex] = true; if (e.ColumnIndex == 0) { e.Value = m_Data[e.RowIndex].Id; } else if (e.ColumnIndex == 1) { e.Value = m_Data[e.RowIndex].Val; } else if (e.ColumnIndex == 2) { Random rand = new Random(); e.Value = rand.Next(); } } private void OnGetVisitedCount(object sender, EventArgs e) { int count = 0; foreach (bool b in m_Visited) { if (b) count++; } MessageBox.Show(count.ToString()); } private void VirtualModeForm_Load(object sender, EventArgs e) { } } public class DataObject { private int m_Id; private int m_Val; public int Val { get { return m_Val; } set { m_Val = value; } } public int Id { get { return m_Id; } set { m_Id = value; } } } }