BaseDataList.DataKeyField Property

 

Gets or sets the key field in the data source specified by the DataSource property.

Namespace:   System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

<ThemeableAttribute(False)>
Public Overridable Property DataKeyField As String

Property Value

Type: System.String

The name of the key field in the data source specified by DataSource.

Use the DataKeyField property to specify the key field in the data source indicated by the DataSource property. The specified field is used to populate the DataKeys collection. This allows you to store the key field with a data listing control without displaying it in the control. The key field is commonly used in a handler for an event, such as ItemCommand or DeleteCommand, as part of an update query string to revise a specific record in the data source. The key field helps the update query string identify the appropriate record to modify.

This property cannot be set by themes or style sheet themes. For more information, see ThemeableAttribute and ASP.NET Themes and Skins.

The following code example demonstrates how to use the DataKeyField property to specify the key field for the data source.


<%@ 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>

.NET Framework
Available since 1.1
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