How to: Implement Virtual Mode in the Windows Forms DataGridView Control
The following code example demonstrates how to manage large sets of data using a DataGridView control with its VirtualMode property set to true.
For a complete explanation of this code example, see Walkthrough: Implementing Virtual Mode in the Windows Forms DataGridView Control.
Example
Imports System
Imports System.Windows.Forms
Public Class Form1
Inherits Form
Private WithEvents dataGridView1 As New DataGridView()
' Declare an ArrayList to serve as the data store.
Private customers As New System.Collections.ArrayList()
' Declare a Customer object to store data for a row being edited.
Private customerInEdit As Customer
' Declare a variable to store the index of a row being edited.
' A value of -1 indicates that there is no row currently in edit.
Private rowInEdit As Integer = -1
' Declare a variable to indicate the commit scope.
' Set this value to false to use cell-level commit scope.
Private rowScopeCommit As Boolean = True
<STAThreadAttribute()> _
Public Shared Sub Main()
Application.Run(New Form1())
End Sub
Public Sub New()
' Initialize the form.
Me.dataGridView1.Dock = DockStyle.Fill
Me.Controls.Add(Me.dataGridView1)
Me.Text = "DataGridView virtual-mode demo (row-level commit scope)"
End Sub
Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) _
Handles Me.Load
' Enable virtual mode.
Me.dataGridView1.VirtualMode = True
' Add columns to the DataGridView.
Dim companyNameColumn As New DataGridViewTextBoxColumn()
With companyNameColumn
.HeaderText = "Company Name"
.Name = "Company Name"
End With
Dim contactNameColumn As New DataGridViewTextBoxColumn()
With contactNameColumn
.HeaderText = "Contact Name"
.Name = "Contact Name"
End With
Me.dataGridView1.Columns.Add(companyNameColumn)
Me.dataGridView1.Columns.Add(contactNameColumn)
Me.dataGridView1.AutoSizeColumnsMode = _
DataGridViewAutoSizeColumnsMode.AllCells
' Add some sample entries to the data store.
Me.customers.Add(New Customer("Bon app'", "Laurence Lebihan"))
Me.customers.Add(New Customer("Bottom-Dollar Markets", _
"Elizabeth Lincoln"))
Me.customers.Add(New Customer("B's Beverages", "Victoria Ashworth"))
' Set the row count, including the row for new records.
Me.dataGridView1.RowCount = 4
End Sub
Private Sub dataGridView1_CellValueNeeded(ByVal sender As Object, _
ByVal e As System.Windows.Forms.DataGridViewCellValueEventArgs) _
Handles dataGridView1.CellValueNeeded
' If this is the row for new records, no values are needed.
If e.RowIndex = Me.dataGridView1.RowCount - 1 Then
Return
End If
Dim customerTmp As Customer = Nothing
' Store a reference to the Customer object for the row being painted.
If e.RowIndex = rowInEdit Then
customerTmp = Me.customerInEdit
Else
customerTmp = CType(Me.customers(e.RowIndex), Customer)
End If
' Set the cell value to paint using the Customer object retrieved.
Select Case Me.dataGridView1.Columns(e.ColumnIndex).Name
Case "Company Name"
e.Value = customerTmp.CompanyName
Case "Contact Name"
e.Value = customerTmp.ContactName
End Select
End Sub
Private Sub dataGridView1_CellValuePushed(ByVal sender As Object, _
ByVal e As System.Windows.Forms.DataGridViewCellValueEventArgs) _
Handles dataGridView1.CellValuePushed
Dim customerTmp As Customer = Nothing
' Store a reference to the Customer object for the row being edited.
If e.RowIndex < Me.customers.Count Then
' If the user is editing a new row, create a new Customer object.
If Me.customerInEdit Is Nothing Then
Me.customerInEdit = New Customer( _
CType(Me.customers(e.RowIndex), Customer).CompanyName, _
CType(Me.customers(e.RowIndex), Customer).ContactName)
End If
customerTmp = Me.customerInEdit
Me.rowInEdit = e.RowIndex
Else
customerTmp = Me.customerInEdit
End If
' Set the appropriate Customer property to the cell value entered.
Dim newValue As String = TryCast(e.Value, String)
Select Case Me.dataGridView1.Columns(e.ColumnIndex).Name
Case "Company Name"
customerTmp.CompanyName = newValue
Case "Contact Name"
customerTmp.ContactName = newValue
End Select
End Sub
Private Sub dataGridView1_NewRowNeeded(ByVal sender As Object, _
ByVal e As System.Windows.Forms.DataGridViewRowEventArgs) _
Handles dataGridView1.NewRowNeeded
' Create a new Customer object when the user edits
' the row for new records.
Me.customerInEdit = New Customer()
Me.rowInEdit = Me.dataGridView1.Rows.Count - 1
End Sub
Private Sub dataGridView1_RowValidated(ByVal sender As Object, _
ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) _
Handles dataGridView1.RowValidated
' Save row changes if any were made and release the edited
' Customer object if there is one.
If e.RowIndex >= Me.customers.Count AndAlso _
e.RowIndex <> Me.dataGridView1.Rows.Count - 1 Then
' Add the new Customer object to the data store.
Me.customers.Add(Me.customerInEdit)
Me.customerInEdit = Nothing
Me.rowInEdit = -1
ElseIf (Me.customerInEdit IsNot Nothing) AndAlso _
e.RowIndex < Me.customers.Count Then
' Save the modified Customer object in the data store.
Me.customers(e.RowIndex) = Me.customerInEdit
Me.customerInEdit = Nothing
Me.rowInEdit = -1
ElseIf Me.dataGridView1.ContainsFocus Then
Me.customerInEdit = Nothing
Me.rowInEdit = -1
End If
End Sub
Private Sub dataGridView1_RowDirtyStateNeeded(ByVal sender As Object, _
ByVal e As System.Windows.Forms.QuestionEventArgs) _
Handles dataGridView1.RowDirtyStateNeeded
If Not rowScopeCommit Then
' In cell-level commit scope, indicate whether the value
' of the current cell has been modified.
e.Response = Me.dataGridView1.IsCurrentCellDirty
End If
End Sub
Private Sub dataGridView1_CancelRowEdit(ByVal sender As Object, _
ByVal e As System.Windows.Forms.QuestionEventArgs) _
Handles dataGridView1.CancelRowEdit
If Me.rowInEdit = Me.dataGridView1.Rows.Count - 2 AndAlso _
Me.rowInEdit = Me.customers.Count Then
' If the user has canceled the edit of a newly created row,
' replace the corresponding Customer object with a new, empty one.
Me.customerInEdit = New Customer()
Else
' If the user has canceled the edit of an existing row,
' release the corresponding Customer object.
Me.customerInEdit = Nothing
Me.rowInEdit = -1
End If
End Sub
Private Sub dataGridView1_UserDeletingRow(ByVal sender As Object, _
ByVal e As System.Windows.Forms.DataGridViewRowCancelEventArgs) _
Handles dataGridView1.UserDeletingRow
If e.Row.Index < Me.customers.Count Then
' If the user has deleted an existing row, remove the
' corresponding Customer object from the data store.
Me.customers.RemoveAt(e.Row.Index)
End If
If e.Row.Index = Me.rowInEdit Then
' If the user has deleted a newly created row, release
' the corresponding Customer object.
Me.rowInEdit = -1
Me.customerInEdit = Nothing
End If
End Sub
End Class
Public Class Customer
Private companyNameValue As String
Private contactNameValue As String
Public Sub New()
' Leave fields empty.
End Sub
Public Sub New(ByVal companyName As String, ByVal contactName As String)
companyNameValue = companyName
contactNameValue = contactName
End Sub
Public Property CompanyName() As String
Get
Return companyNameValue
End Get
Set(ByVal value As String)
companyNameValue = value
End Set
End Property
Public Property ContactName() As String
Get
Return contactNameValue
End Get
Set(ByVal value As String)
contactNameValue = value
End Set
End Property
End Class
using System;
using System.Windows.Forms;
public class Form1 : Form
{
private DataGridView dataGridView1 = new DataGridView();
// Declare an ArrayList to serve as the data store.
private System.Collections.ArrayList customers =
new System.Collections.ArrayList();
// Declare a Customer object to store data for a row being edited.
private Customer customerInEdit;
// Declare a variable to store the index of a row being edited.
// A value of -1 indicates that there is no row currently in edit.
private int rowInEdit = -1;
// Declare a variable to indicate the commit scope.
// Set this value to false to use cell-level commit scope.
private bool rowScopeCommit = true;
[STAThreadAttribute()]
public static void Main()
{
Application.Run(new Form1());
}
public Form1()
{
// Initialize the form.
this.dataGridView1.Dock = DockStyle.Fill;
this.Controls.Add(this.dataGridView1);
this.Load += new EventHandler(Form1_Load);
this.Text = "DataGridView virtual-mode demo (row-level commit scope)";
}
private void Form1_Load(object sender, EventArgs e)
{
// Enable virtual mode.
this.dataGridView1.VirtualMode = true;
// Connect the virtual-mode events to event handlers.
this.dataGridView1.CellValueNeeded += new
DataGridViewCellValueEventHandler(dataGridView1_CellValueNeeded);
this.dataGridView1.CellValuePushed += new
DataGridViewCellValueEventHandler(dataGridView1_CellValuePushed);
this.dataGridView1.NewRowNeeded += new
DataGridViewRowEventHandler(dataGridView1_NewRowNeeded);
this.dataGridView1.RowValidated += new
DataGridViewCellEventHandler(dataGridView1_RowValidated);
this.dataGridView1.RowDirtyStateNeeded += new
QuestionEventHandler(dataGridView1_RowDirtyStateNeeded);
this.dataGridView1.CancelRowEdit += new
QuestionEventHandler(dataGridView1_CancelRowEdit);
this.dataGridView1.UserDeletingRow += new
DataGridViewRowCancelEventHandler(dataGridView1_UserDeletingRow);
// Add columns to the DataGridView.
DataGridViewTextBoxColumn companyNameColumn = new
DataGridViewTextBoxColumn();
companyNameColumn.HeaderText = "Company Name";
companyNameColumn.Name = "Company Name";
DataGridViewTextBoxColumn contactNameColumn = new
DataGridViewTextBoxColumn();
contactNameColumn.HeaderText = "Contact Name";
contactNameColumn.Name = "Contact Name";
this.dataGridView1.Columns.Add(companyNameColumn);
this.dataGridView1.Columns.Add(contactNameColumn);
this.dataGridView1.AutoSizeColumnsMode =
DataGridViewAutoSizeColumnsMode.AllCells;
// Add some sample entries to the data store.
this.customers.Add(new Customer(
"Bon app'", "Laurence Lebihan"));
this.customers.Add(new Customer(
"Bottom-Dollar Markets", "Elizabeth Lincoln"));
this.customers.Add(new Customer(
"B's Beverages", "Victoria Ashworth"));
// Set the row count, including the row for new records.
this.dataGridView1.RowCount = 4;
}
private void dataGridView1_CellValueNeeded(object sender,
System.Windows.Forms.DataGridViewCellValueEventArgs e)
{
// If this is the row for new records, no values are needed.
if (e.RowIndex == this.dataGridView1.RowCount - 1) return;
Customer customerTmp = null;
// Store a reference to the Customer object for the row being painted.
if (e.RowIndex == rowInEdit)
{
customerTmp = this.customerInEdit;
}
else
{
customerTmp = (Customer)this.customers[e.RowIndex];
}
// Set the cell value to paint using the Customer object retrieved.
switch (this.dataGridView1.Columns[e.ColumnIndex].Name)
{
case "Company Name":
e.Value = customerTmp.CompanyName;
break;
case "Contact Name":
e.Value = customerTmp.ContactName;
break;
}
}
private void dataGridView1_CellValuePushed(object sender,
System.Windows.Forms.DataGridViewCellValueEventArgs e)
{
Customer customerTmp = null;
// Store a reference to the Customer object for the row being edited.
if (e.RowIndex < this.customers.Count)
{
// If the user is editing a new row, create a new Customer object.
if (this.customerInEdit == null)
{
this.customerInEdit = new Customer(
((Customer)this.customers[e.RowIndex]).CompanyName,
((Customer)this.customers[e.RowIndex]).ContactName);
}
customerTmp = this.customerInEdit;
this.rowInEdit = e.RowIndex;
}
else
{
customerTmp = this.customerInEdit;
}
// Set the appropriate Customer property to the cell value entered.
String newValue = e.Value as String;
switch (this.dataGridView1.Columns[e.ColumnIndex].Name)
{
case "Company Name":
customerTmp.CompanyName = newValue;
break;
case "Contact Name":
customerTmp.ContactName = newValue;
break;
}
}
private void dataGridView1_NewRowNeeded(object sender,
System.Windows.Forms.DataGridViewRowEventArgs e)
{
// Create a new Customer object when the user edits
// the row for new records.
this.customerInEdit = new Customer();
this.rowInEdit = this.dataGridView1.Rows.Count - 1;
}
private void dataGridView1_RowValidated(object sender,
System.Windows.Forms.DataGridViewCellEventArgs e)
{
// Save row changes if any were made and release the edited
// Customer object if there is one.
if (e.RowIndex >= this.customers.Count &&
e.RowIndex != this.dataGridView1.Rows.Count - 1)
{
// Add the new Customer object to the data store.
this.customers.Add(this.customerInEdit);
this.customerInEdit = null;
this.rowInEdit = -1;
}
else if (this.customerInEdit != null &&
e.RowIndex < this.customers.Count)
{
// Save the modified Customer object in the data store.
this.customers[e.RowIndex] = this.customerInEdit;
this.customerInEdit = null;
this.rowInEdit = -1;
}
else if (this.dataGridView1.ContainsFocus)
{
this.customerInEdit = null;
this.rowInEdit = -1;
}
}
private void dataGridView1_RowDirtyStateNeeded(object sender,
System.Windows.Forms.QuestionEventArgs e)
{
if (!rowScopeCommit)
{
// In cell-level commit scope, indicate whether the value
// of the current cell has been modified.
e.Response = this.dataGridView1.IsCurrentCellDirty;
}
}
private void dataGridView1_CancelRowEdit(object sender,
System.Windows.Forms.QuestionEventArgs e)
{
if (this.rowInEdit == this.dataGridView1.Rows.Count - 2 &&
this.rowInEdit == this.customers.Count)
{
// If the user has canceled the edit of a newly created row,
// replace the corresponding Customer object with a new, empty one.
this.customerInEdit = new Customer();
}
else
{
// If the user has canceled the edit of an existing row,
// release the corresponding Customer object.
this.customerInEdit = null;
this.rowInEdit = -1;
}
}
private void dataGridView1_UserDeletingRow(object sender,
System.Windows.Forms.DataGridViewRowCancelEventArgs e)
{
if (e.Row.Index < this.customers.Count)
{
// If the user has deleted an existing row, remove the
// corresponding Customer object from the data store.
this.customers.RemoveAt(e.Row.Index);
}
if (e.Row.Index == this.rowInEdit)
{
// If the user has deleted a newly created row, release
// the corresponding Customer object.
this.rowInEdit = -1;
this.customerInEdit = null;
}
}
}
public class Customer
{
private String companyNameValue;
private String contactNameValue;
public Customer()
{
// Leave fields empty.
}
public Customer(String companyName, String contactName)
{
companyNameValue = companyName;
contactNameValue = contactName;
}
public String CompanyName
{
get
{
return companyNameValue;
}
set
{
companyNameValue = value;
}
}
public String ContactName
{
get
{
return contactNameValue;
}
set
{
contactNameValue = value;
}
}
}
Compiling the Code
This example requires:
- References to the System and System.Windows.Forms assemblies.
For information about building this example from the command line for Visual Basic or Visual C#, see Building from the Command Line (Visual Basic) or Command-Line Building. You can also build this example in Visual Studio by pasting the code into a new project. How to: Compile and Run a Complete Windows Forms Code Example Using Visual Studio
How to: Compile and Run a Complete Windows Forms Code Example Using Visual Studio
How to: Compile and Run a Complete Windows Forms Code Example Using Visual Studio
How to: Compile and Run a Complete Windows Forms Code Example Using Visual Studio
See Also
Tasks
Walkthrough: Implementing Virtual Mode in the Windows Forms DataGridView Control
Reference
DataGridView
VirtualMode
CellValueNeeded
CellValuePushed
NewRowNeeded
RowValidated
RowDirtyStateNeeded
CancelRowEdit
UserDeletingRow
Concepts
Virtual Mode in the Windows Forms DataGridView Control
Other Resources
Performance Tuning in the Windows Forms DataGridView Control