DataGridView.VirtualMode Propiedad
Definición
Importante
Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.
Obtiene o establece un valor que indica si ha proporcionado sus propias operaciones de administración de datos para el DataGridView control.
public:
property bool VirtualMode { bool get(); void set(bool value); };public bool VirtualMode { get; set; }member this.VirtualMode : bool with get, setPublic Property VirtualMode As BooleanValor de propiedad
true
DataGridView si usa operaciones de administración de datos que proporcione; de lo contrario, false. El valor predeterminado es false.
Ejemplos
El código de ejemplo de código siguiente usa el modo virtual para crear una tabla de enteros positivos.
using System.IO;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Drawing;
using System;
public class VirtualModeDemo : Form
{
DataGridView dataGridView1 = new DataGridView();
public VirtualModeDemo()
: base()
{
Text = "DataGridView virtual-mode demo (cell-level commit scope)";
dataGridView1.NewRowNeeded +=
new DataGridViewRowEventHandler(dataGridView1_NewRowNeeded);
dataGridView1.RowsAdded +=
new DataGridViewRowsAddedEventHandler(dataGridView1_RowsAdded);
dataGridView1.CellValidating +=
new DataGridViewCellValidatingEventHandler(dataGridView1_CellValidating);
dataGridView1.CellValueNeeded +=
new DataGridViewCellValueEventHandler(dataGridView1_CellValueNeeded);
dataGridView1.CellValuePushed +=
new DataGridViewCellValueEventHandler(dataGridView1_CellValuePushed);
Controls.Add(dataGridView1);
dataGridView1.VirtualMode = true;
dataGridView1.AllowUserToDeleteRows = false;
dataGridView1.Columns.Add("Numbers", "Positive Numbers");
dataGridView1.Rows.AddCopies(0, initialSize);
}
bool newRowNeeded;
private void dataGridView1_NewRowNeeded(object sender,
DataGridViewRowEventArgs e)
{
newRowNeeded = true;
}
const int initialSize = 5000000;
int numberOfRows = initialSize;
private void dataGridView1_RowsAdded(object sender,
DataGridViewRowsAddedEventArgs e)
{
if (newRowNeeded)
{
newRowNeeded = false;
numberOfRows = numberOfRows + 1;
}
}
#region "data store maintance"
const int initialValue = -1;
private void dataGridView1_CellValueNeeded(object sender,
DataGridViewCellValueEventArgs e)
{
if (store.ContainsKey(e.RowIndex))
{
// Use the store if the e value has been modified
// and stored.
e.Value = store[e.RowIndex];
}
else if (newRowNeeded && e.RowIndex == numberOfRows)
{
if (dataGridView1.IsCurrentCellInEditMode)
{
e.Value = initialValue;
}
else
{
// Show a blank value if the cursor is just resting
// on the last row.
e.Value = String.Empty;
}
}
else
{
e.Value = e.RowIndex;
}
}
private void dataGridView1_CellValuePushed(object sender,
DataGridViewCellValueEventArgs e)
{
store.Add(e.RowIndex, int.Parse(e.Value.ToString()));
}
#endregion
private Dictionary<int, int> store = new Dictionary<int, int>();
private void dataGridView1_CellValidating(object sender,
DataGridViewCellValidatingEventArgs e)
{
dataGridView1.Rows[e.RowIndex].ErrorText = "";
int newInteger;
// Don't try to validate the 'new row' until finished
// editing since there
// is not any point in validating its initial value.
if (dataGridView1.Rows[e.RowIndex].IsNewRow) { return; }
if (!int.TryParse(e.FormattedValue.ToString(),
out newInteger) || newInteger < 0)
{
e.Cancel = true;
dataGridView1.Rows[e.RowIndex].ErrorText = "the value must be a non-negative integer";
}
}
[STAThreadAttribute()]
public static void Main()
{
Application.Run(new VirtualModeDemo());
}
}
Imports System.IO
Imports System.Collections.Generic
Imports System.Windows.Forms
Public Class VirtualModeDemo
Inherits System.Windows.Forms.Form
Dim WithEvents dataGridView1 As New DataGridView
Public Sub New()
MyBase.New()
Text = "DataGridView virtual-mode demo (cell-level commit scope)"
Controls.Add(dataGridView1)
dataGridView1.VirtualMode = True
dataGridView1.AllowUserToDeleteRows = False
dataGridView1.Columns.Add("Numbers", "Positive Numbers")
dataGridView1.Rows.AddCopies(0, initialSize)
End Sub
Dim newRowNeeded As Boolean
Private Sub dataGridView1_NewRowNeeded(ByVal sender As Object, _
ByVal e As DataGridViewRowEventArgs) _
Handles dataGridView1.NewRowNeeded
newRowNeeded = True
End Sub
Const initialSize As Integer = 5000000
Dim numberOfRows As Integer = initialSize
Private Sub dataGridView1_RowsAdded(ByVal sender As Object, _
ByVal e As DataGridViewRowsAddedEventArgs) _
Handles dataGridView1.RowsAdded
If newRowNeeded Then
newRowNeeded = False
numberOfRows = numberOfRows + 1
End If
End Sub
#Region "data store maintance"
Const initialValue As Integer = -1
Private Sub dataGridView1_CellValueNeeded(ByVal sender As Object, _
ByVal e As DataGridViewCellValueEventArgs) _
Handles dataGridView1.CellValueNeeded
If store.ContainsKey(e.RowIndex) Then
' Use the store if the e value has been modified
' and stored.
e.Value = store(e.RowIndex)
ElseIf newRowNeeded AndAlso e.RowIndex = numberOfRows Then
If dataGridView1.IsCurrentCellInEditMode Then
e.Value = initialValue
Else
' Show a blank value if the cursor is just resting
' on the last row.
e.Value = String.Empty
End If
Else
e.Value = e.RowIndex
End If
End Sub
Private Sub dataGridView1_CellValuePushed(ByVal sender As Object, _
ByVal e As DataGridViewCellValueEventArgs) _
Handles dataGridView1.CellValuePushed
store.Add(e.RowIndex, CInt(e.Value))
End Sub
#End Region
Dim store As System.Collections.Generic.Dictionary(Of Integer, Integer) = _
New Dictionary(Of Integer, Integer)
Private Sub dataGridView1_CellValidating(ByVal sender As Object, _
ByVal e _
As DataGridViewCellValidatingEventArgs) _
Handles dataGridView1.CellValidating
Me.dataGridView1.Rows(e.RowIndex).ErrorText = ""
Dim newInteger As Integer
' Don't try to validate the 'new row' until finished
' editing since there
' is not any point in validating its initial value.
If dataGridView1.Rows(e.RowIndex).IsNewRow Then Return
If Not Integer.TryParse(e.FormattedValue.ToString(), newInteger) _
OrElse newInteger < 0 Then
e.Cancel = True
Me.dataGridView1.Rows(e.RowIndex).ErrorText = "the value must be a non-negative integer"
End If
End Sub
<STAThreadAttribute()> _
Public Shared Sub Main()
Application.Run(New VirtualModeDemo())
End Sub
End Class
Comentarios
El modo virtual está diseñado para su uso con grandes almacenes de datos. Cuando la VirtualMode propiedad es true, se crea con DataGridView un número establecido de filas y columnas y, a continuación, se controla el CellValueNeeded evento para rellenar las celdas. El modo virtual requiere la implementación de una caché de datos subyacente para controlar el rellenado, la edición y la eliminación de celdas en función de DataGridView las acciones del usuario. Para obtener más información sobre cómo implementar el modo virtual, vea Cómo: Implementar el modo virtual en el control DataGridView de formularios Windows Forms.
Debe usar el modo virtual para mantener los valores de las columnas desenlace cuando el DataGridView control está en modo enlazado. No se admite la ordenación por columnas sin enlazar en modo enlazado.
