DataGrid.VirtualItemCount Eigenschaft

Referenz

Definition

Namespace:: System.Web.UI.WebControls

Assembly:: System.Web.dll

Wichtig

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Ruft bei Verwendung von benutzerdefiniertem Paging die virtuelle Anzahl von Elementen im DataGrid-Steuerelement ab oder legt diese fest.

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

Eigenschaftswert

Int32

Die virtuelle Anzahl von Elementen im DataGrid-Steuerelement, wenn das benutzerdefinierte Paging verwendet wird.

Attribute: BrowsableAttribute

Ausnahmen

ArgumentOutOfRangeException

Der angegebene Wert ist eine negative Zahl.

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie die VirtualItemCount -Eigenschaft verwendet wird, um die Gesamtzahl der Elemente im DataGrid Steuerelement anzugeben, wenn benutzerdefiniertes Paging verwendet wird.

<%@ 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>

Hinweise

Verwenden Sie diese Eigenschaft, um die virtuelle Anzahl von Elementen im DataGrid Steuerelement anzugeben, wenn benutzerdefiniertes Paging verwendet wird. Diese Eigenschaft wird nur verwendet, wenn die AllowCustomPaging -Eigenschaft auf truefestgelegt ist.

Wenn die AllowCustomPaging -Eigenschaft auf truefestgelegt ist, wird die Anzahl der Seiten, die DataGrid zum Anzeigen jedes Elements im Steuerelement erforderlich sind, basierend auf den Werten der PageSize Eigenschaften und VirtualItemCount berechnet.

Wenn die AllowCustomPaging -Eigenschaft auf falsefestgelegt ist, wird die Anzahl der im DataGrid Steuerelement angezeigten Seiten basierend auf den Werten der PageSize -Eigenschaft und der Gesamtzahl der Elemente in der Datenquelle berechnet.

Gilt für: