DataKeyCollection.Item プロパティとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

DataKeyCollection.Item プロパティ

コレクション内の指定したインデックス位置にあるキーフィールドを取得します。

名前空間: System.Web.UI.WebControls
アセンブリ: System.Web (system.web.dll 内)
構文

Visual Basic (宣言)

Public ReadOnly Default
 Property Item ( _
    index As Integer _
) As Object

Visual Basic (使用法)

Dim instance As DataKeyCollection
Dim index As Integer
Dim value As Object

value = instance(index)

public Object this [
    int index
] { get; }

C++

public:
property Object^ default [int] {
    Object^ get (int index);
}

/** @property */
public Object get_Item (int index)

JScript

JScript では、インデックス付きのプロパティは使用できますが、新規に宣言することはできません。.

パラメータ

index: コレクションから取得するキーフィールドの 0 から始まるインデックス番号。

プロパティ値
コレクション内の指定したインデックス位置にあるキーフィールド。

解説

このインデクサを使用して、配列表記で指定したインデックス位置にある DataKeyCollection のキーフィールドを取得します。

使用例

Visual Basic

<%@ Page Language="VB" AutoEventWireup="True"
 %>
<%@ Import Namespace="System.Data"
 %>

<html>

<head>

   <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 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>

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

<html>

<head>

   <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 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>