DataGridView.VirtualMode DataGridView.VirtualMode DataGridView.VirtualMode DataGridView.VirtualMode Property

定义

获取或设置一个值,该值指示你是否为 DataGridView 控件提供了自己的数据管理操作。Gets or sets a value indicating whether you have provided your own data-management operations for the DataGridView control.

public:
 property bool VirtualMode { bool get(); void set(bool value); };
public bool VirtualMode { get; set; }
member this.VirtualMode : bool with get, set
Public Property VirtualMode As Boolean

属性值

如果true 使用你所提供的数据管理操作,则为 DataGridView ;否则为 falsetrue if the DataGridView uses data-management operations that you provide; otherwise, false. 默认值为 falseThe default is false.

示例

下面的代码示例使用虚拟模式创建正整数表。The following code example code uses virtual mode to create a table of positive integers.

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

注解

虚拟模式适用于大数据存储。Virtual mode is designed for use with very large stores of data. 当属性为true时,您创建DataGridView具有设置CellValueNeeded的行数和列数的,然后处理事件以填充单元格。 VirtualModeWhen the VirtualMode property is true, you create a DataGridView with a set number of rows and columns and then handle the CellValueNeeded event to populate the cells. 虚拟模式要求基础数据缓存的实现基于用户的操作来处理DataGridView单元的填充、编辑和删除。Virtual mode requires implementation of an underlying data cache to handle the population, editing, and deletion of DataGridView cells based on actions of the user. 有关实现虚拟模式的详细信息,请参阅如何:在 Windows 窗体 DataGridView 控件中实现虚拟模式。For more information about implementing virtual mode, see How to: Implement Virtual Mode in the Windows Forms DataGridView Control.

DataGridView控件处于绑定模式时,必须使用虚拟模式来维护未绑定列的值。You must use virtual mode to maintain the values of unbound columns when the DataGridView control is in bound mode. 不支持在绑定模式下按未绑定列进行排序。Sorting by unbound columns in bound mode is not supported.

适用于

另请参阅