DataGrid.VirtualItemCount Özellik
Tanım
Önemli
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Özel disk belleği kullanıldığında denetimdeki DataGrid sanal öğe sayısını alır veya ayarlar.
public:
virtual property int VirtualItemCount { int get(); void set(int value); };
[System.ComponentModel.Browsable(false)]
public virtual int VirtualItemCount { get; set; }
[<System.ComponentModel.Browsable(false)>]
member this.VirtualItemCount : int with get, set
Public Overridable Property VirtualItemCount As Integer
Özellik Değeri
Özel disk belleği kullanıldığında denetimdeki DataGrid öğelerin sanal sayısı.
- Öznitelikler
Özel durumlar
Belirtilen değer negatif bir sayıdır.
Örnekler
Aşağıdaki kod örneği, özel disk belleği kullanıldığında denetimdeki DataGrid öğelerin toplam sayısını belirtmek için özelliğinin nasıl VirtualItemCount kullanılacağını gösterir.
<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<script runat="server">
// Normally, an entire data source is loaded in the DataGrid control,
// which can take up a lot of resources. This example uses custom
// paging, which loads only the segment of data needed to fill a
// single page. In order to query for the appropriate segment of
// data, the index of the first item displayed on a page must be
// tracked as the user navigates between pages.
int startIndex = 0;
ICollection CreateDataSource()
{
// Create sample data for the DataGrid control.
DataTable dt = new DataTable();
DataRow dr;
// Define the columns of the table.
dt.Columns.Add(new DataColumn("IntegerValue", typeof(Int32)));
dt.Columns.Add(new DataColumn("StringValue", typeof(string)));
dt.Columns.Add(new DataColumn("DateTimeValue", typeof(string)));
dt.Columns.Add(new DataColumn("BoolValue", typeof(bool)));
// Populate the table with sample values. When using custom paging,
// a query should only return enough data to fill a single page,
// beginning at the start index.
for (int i = startIndex; i < (startIndex + MyDataGrid.PageSize); i++)
{
dr = dt.NewRow();
dr[0] = i;
dr[1] = "Item " + i.ToString();
dr[2] = DateTime.Now.ToShortDateString();
dr[3] = (i % 2 != 0) ? true : false;
dt.Rows.Add(dr);
}
DataView dv = new DataView(dt);
return dv;
}
void Page_Load(Object sender, EventArgs e)
{
// Load sample data only once, when the page is first loaded.
if (!IsPostBack)
{
// Set the virtual item count, which specifies the total number
// items displayed in the DataGrid control when custom paging
// is used.
MyDataGrid.VirtualItemCount = 200;
// Retrieve the segment of data to display on the page from the
// data source and bind it to the DataGrid control.
BindGrid();
}
}
void MyDataGrid_Page(Object sender, DataGridPageChangedEventArgs e)
{
// For the DataGrid control to navigate to the correct page when
// paging is allowed, the CurrentPageIndex property must be updated
// programmatically. This process is usually accomplished in the
// event-handling method for the PageIndexChanged event.
// Set CurrentPageIndex to the page the user clicked.
MyDataGrid.CurrentPageIndex = e.NewPageIndex;
// Calculate the index of the first item to display on the page
// using the current page index and the page size.
startIndex = MyDataGrid.CurrentPageIndex * MyDataGrid.PageSize;
// Retrieve the segment of data to display on the page from the
// data source and bind it to the DataGrid control.
BindGrid();
}
void BindGrid()
{
MyDataGrid.DataSource = CreateDataSource();
MyDataGrid.DataBind();
}
</script>
<head runat="server">
<title> DataGrid Custom Paging Example </title>
</head>
<body>
<form id="form1" runat="server">
<h3> DataGrid Custom Paging Example </h3>
<asp:DataGrid id="MyDataGrid"
AllowCustomPaging="True"
AllowPaging="True"
PageSize="10"
OnPageIndexChanged="MyDataGrid_Page"
runat="server">
<HeaderStyle BackColor="Navy"
ForeColor="White"
Font-Bold="True" />
<PagerStyle Mode="NumericPages"
HorizontalAlign="Right" />
</asp:DataGrid>
</form>
</body>
</html>
<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<script runat="server">
' Normally, an entire data source is loaded in the DataGrid control,
' which can take up a lot of resources. This example uses custom
' paging, which loads only the segment of data needed to fill a
' single page. In order to query for the appropriate segment of
' data, the index of the first item displayed on a page must be
' tracked as the user navigates between pages.
Dim startIndex As Integer = 0
Function CreateDataSource() As ICollection
' Create sample data for the DataGrid control.
Dim dt As DataTable = New DataTable()
Dim dr As DataRow
' Define the columns of the table.
dt.Columns.Add(New DataColumn("IntegerValue", GetType(Int32)))
dt.Columns.Add(New DataColumn("StringValue", GetType(String)))
dt.Columns.Add(New DataColumn("DateTimeValue", GetType(String)))
dt.Columns.Add(New DataColumn("BoolValue", GetType(Boolean)))
' Populate the table with sample values. When using custom paging,
' a query should only return enough data to fill a single page,
' beginning at the start index.
Dim i As Integer
For i = startIndex To ((startIndex + MyDataGrid.PageSize) - 1)
dr = dt.NewRow()
dr(0) = i
dr(1) = "Item " & i.ToString()
dr(2) = DateTime.Now.ToShortDateString()
If (i Mod 2 <> 0) Then
dr(3) = True
Else
dr(3) = False
End If
dt.Rows.Add(dr)
Next i
Dim dv As DataView = New DataView(dt)
Return dv
End Function
Sub Page_Load(sender As Object, e As EventArgs)
' Load sample data only once, when the page is first loaded.
If Not IsPostBack Then
' Set the virtual item count, which specifies the total number
' items displayed in the DataGrid control when custom paging
' is used.
MyDataGrid.VirtualItemCount = 200
' Retrieve the segment of data to display on the page from the
' data source and bind it to the DataGrid control.
BindGrid()
End If
End Sub
Sub MyDataGrid_Page(sender as Object, e As DataGridPageChangedEventArgs)
' For the DataGrid control to navigate to the correct page when
' paging is allowed, the CurrentPageIndex property must be updated
' programmatically. This process is usually accomplished in the
' event-handling method for the PageIndexChanged event.
' Set CurrentPageIndex to the page the user clicked.
MyDataGrid.CurrentPageIndex = e.NewPageIndex
' Calculate the index of the first item to display on the page
' using the current page index and the page size.
startIndex = MyDataGrid.CurrentPageIndex * MyDataGrid.PageSize
' Retrieve the segment of data to display on the page from the
' data source and bind it to the DataGrid control.
BindGrid()
End Sub
Sub BindGrid()
MyDataGrid.DataSource = CreateDataSource()
MyDataGrid.DataBind()
End Sub
</script>
<head runat="server">
<title> DataGrid Custom Paging Example </title>
</head>
<body>
<form id="form1" runat="server">
<h3> DataGrid Custom Paging Example </h3>
<asp:DataGrid id="MyDataGrid"
AllowCustomPaging="True"
AllowPaging="True"
PageSize="10"
OnPageIndexChanged="MyDataGrid_Page"
runat="server">
<HeaderStyle BackColor="Navy"
ForeColor="White"
Font-Bold="True" />
<PagerStyle Mode="NumericPages"
HorizontalAlign="Right" />
</asp:DataGrid>
</form>
</body>
</html>
Açıklamalar
Özel disk belleği kullanıldığında denetimdeki DataGrid öğelerin sanal sayısını belirtmek için bu özelliği kullanın. Bu özellik yalnızca özelliği olarak true
ayarlandığında kullanılırAllowCustomPaging.
AllowCustomPaging özelliği olarak true
ayarlanırsa, denetimdeki DataGrid her öğeyi görüntülemek için gereken sayfa sayısı ve VirtualItemCount özelliklerinin değerlerine PageSize göre hesaplanır.
AllowCustomPaging özelliği olarak false
ayarlanırsa, denetimde DataGrid görüntülenen sayfa sayısı özelliğin PageSize değerlerine ve veri kaynağındaki toplam öğe sayısına göre hesaplanır.