BaseDataList.DataKeys Eigenschaft

  • Referenz

Definition

Namespace:
System.Web.UI.WebControls
Assembly:
System.Web.dll

Ruft ein DataKeyCollection-Objekt ab, in dem die Schlüsselwerte aller Datensätze in einem Datenauflistungssteuerelement gespeichert sind.

public:
 property System::Web::UI::WebControls::DataKeyCollection ^ DataKeys { System::Web::UI::WebControls::DataKeyCollection ^ get(); };
[System.ComponentModel.Browsable(false)]
public System.Web.UI.WebControls.DataKeyCollection DataKeys { get; }
[<System.ComponentModel.Browsable(false)>]
member this.DataKeys : System.Web.UI.WebControls.DataKeyCollection
Public ReadOnly Property DataKeys As DataKeyCollection

Eigenschaftswert

DataKeyCollection

Eine DataKeyCollection, in der die Schlüsselwerte aller Datensätze in einem Datenauflistungssteuerelement gespeichert sind.

Attribute
BrowsableAttribute

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie sie mithilfe der DataKeys -Eigenschaft den Wert des Schlüsselfelds für den zu löschenden Datensatz bestimmen.


<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

<!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" >

<head runat="server">
    <title>BaseDataList DataKeys Example</title>
<script runat="server">

      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("CurrencyValue", typeof(double)));

         // Define the primary key for the table as the IntegerValue 
         // column (column 0). To do this, first create an array of 
         // DataColumns to represent the primary key. The primary key can
         // consist of multiple columns, but in this example, only
         // one column is used.
         DataColumn[] keys = new DataColumn[1];
         keys[0] = dt.Columns[0];

         // Then assign the array to the PrimaryKey property of the DataTable. 
         dt.PrimaryKey = keys;
 
         // Populate the table with sample values.
         for (int i = 0; i < 9; i++) 
         {
            dr = dt.NewRow();
 
            dr[0] = i;
            dr[1] = "Item " + i.ToString();
            dr[2] = 1.23 * (i + 1);
 
            dt.Rows.Add(dr);
         }

         // To persist the data source between posts to the server, 
         // store it in session state.  
         Session["Source"] = dt;
 
         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) 
         {
            ItemsGrid.DataSource = CreateDataSource();
            ItemsGrid.DataBind();
         }

      }

      void Delete_Command(Object sender, DataGridCommandEventArgs e)
      {

         // Retrieve the data table from session state.
         DataTable dt = (DataTable)Session["Source"];

         // Retrieve the data row to delete from the data table. 
         // Use the DataKeys property of the DataGrid control to get 
         // the primary key value of the selected row. 
         // Search the Rows collection of the data table for this value. 
         DataRow row;
         row = dt.Rows.Find(ItemsGrid.DataKeys[e.Item.ItemIndex]);

         // Delete the item selected in the DataGrid from the data source.
         if(row != null)
         {
            dt.Rows.Remove(row);
         }

         // Save the data source.
         Session["Source"] = dt;

         // Create a DataView and bind it to the DataGrid control.
         DataView dv = new DataView(dt);
         ItemsGrid.DataSource = dv;
         ItemsGrid.DataBind();

      }

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3>BaseDataList DataKeys Example</h3>

      <asp:DataGrid id="ItemsGrid" 
           BorderColor="Black"
           ShowFooter="False" 
           CellPadding="3" 
           CellSpacing="0"
           HeaderStyle-BackColor="#aaaadd"
           DataKeyField="IntegerValue"
           OnDeleteCommand="Delete_Command"
           runat="server">

         <Columns>

            <asp:ButtonColumn Text="Delete"
                 CommandName="Delete"/>

         </Columns>

      </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" >

<head runat="server">
    <title>BaseDataList DataKeys and DataKeyField Example</title>
<script runat="server">

      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(Integer)))
         dt.Columns.Add(new DataColumn("StringValue", GetType(String)))
         dt.Columns.Add(new DataColumn("CurrencyValue", GetType(Double)))

         ' Define the primary key for the table as the IntegerValue 
         ' column (column 0). To do this, first create an array of 
         ' DataColumns to represent the primary key. The primary key can
         ' consist of multiple columns, but in this example, only
         ' one column is used.
         Dim keys(1) As DataColumn
         keys(0) = dt.Columns(0)

         ' Then assign the array to the PrimaryKey property of the DataTable. 
         dt.PrimaryKey = keys
 
         ' Populate the table with sample values.
         Dim i As Integer

         For i = 0 To 8 
     
            dr = dt.NewRow()
 
            dr(0) = i
            dr(1) = "Item " & i.ToString()
            dr(2) = 1.23 * (i + 1)
 
            dt.Rows.Add(dr)

         Next

         ' To persist the data source between posts to the server, 
         ' store it in session state.  
         Session("Source") = dt
 
         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 
        
            ItemsGrid.DataSource = CreateDataSource()
            ItemsGrid.DataBind()
         
         End If

      End Sub

      Sub Delete_Command(sender As Object, e As DataGridCommandEventArgs)

         ' Retrieve the data table from session state.
         Dim dt As DataTable = CType(Session("Source"), DataTable)

         ' Retrieve the data row to delete from the data table. 
         ' Use the DataKeys property of the DataGrid control to get 
         ' the primary key value of the selected row. 
         ' Search the Rows collection of the data table for this value. 
         Dim row As DataRow
         row = dt.Rows.Find(ItemsGrid.DataKeys(e.Item.ItemIndex))

         ' Delete the item selected in the DataGrid from the data source.
         If Not row is Nothing Then
         
            dt.Rows.Remove(row)
         
         End If

         ' Save the data source.
         Session("Source") = dt

         ' Create a DataView and bind it to the DataGrid control.
         Dim dv As DataView = New DataView(dt)
         ItemsGrid.DataSource = dv
         ItemsGrid.DataBind()

      End Sub

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3>BaseDataList DataKeys and DataKeyField Example</h3>

      <asp:DataGrid id="ItemsGrid" 
           BorderColor="Black"
           ShowFooter="False" 
           CellPadding="3" 
           CellSpacing="0"
           HeaderStyle-BackColor="#aaaadd"
           DataKeyField="IntegerValue"
           OnDeleteCommand="Delete_Command"
           runat="server">

         <Columns>

            <asp:ButtonColumn Text="Delete"
                 CommandName="Delete"/>

         </Columns>

      </asp:DataGrid>

   </form>

</body>
</html>

Hinweise

Verwenden Sie die DataKeys Auflistung, um auf die Schlüsselwerte jedes Datensatzes (als Zeile angezeigt) in einem Datenauflistungssteuerelement zuzugreifen. Dadurch können Sie das Schlüsselfeld mit einem Datenauflistungssteuerelement speichern, ohne es im Steuerelement anzuzeigen. Diese Auflistung wird automatisch mit den Werten aus dem von der DataKeyField -Eigenschaft angegebenen Feld gefüllt.

Das Schlüsselfeld wird häufig in einem Handler für ein Ereignis wie oder DeleteCommandals Teil einer Updateabfragezeichenfolge verwendet, ItemCommand um einen bestimmten Datensatz in der Datenquelle zu überarbeiten. Das Schlüsselfeld hilft der Aktualisierungsabfragezeichenfolge dabei, den entsprechenden zu ändernden Datensatz zu identifizieren.

Weitere Informationen zum Zugriff auf Daten mit ASP.NET finden Sie unter ASP.NET Datenzugriffsinhaltszuordnung.

Gilt für:

Weitere Informationen