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

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DataKeyArray.Count プロパティ

メモ : このプロパティは、.NET Framework version 2.0 で新しく追加されたものです。

コレクション内の項目の数を取得します。

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 Property
 Count As Integer

Visual Basic (使用法)

Dim instance As DataKeyArray
Dim value As Integer

value = instance.Count

public int Count { get;
 }

C++

public:
virtual property int Count {
    int get () sealed;
}

/** @property */
public final int get_Count ()

JScript

public final function get
 Count () : int

プロパティ値
コレクション内の項目の数。

解説

コレクション内の項目の数を確認するには、Count プロパティを使用します。通常、Count プロパティは、コレクションを反復処理して上限を確認する場合に使用されます。Count プロパティは、コレクションが空であるかどうかを確認する場合にも一般に使用されます。

使用例

Count プロパティを使用して、DataKeyArray コレクションが空かどうかを確認するコード例を次に示します。

Visual Basic

<%@ Page language="VB" %>

<script runat="server">

  Sub CustomerGridView_DataBound(ByVal sender
 As Object, ByVal e As
 EventArgs) Handles CustomerGridView.DataBound

    ' Use the Count property to determine whether the
    ' DataKeys collection contains any items.
    If CustomerGridView.DataKeys.Count > 0 Then

      MessageLabel.Text = "The primary key of each record displayed
 are: <br/><br/>"

      ' Use the GetEnumerator method to create an enumerator that 
      ' contains the DataKey objects for the GridView control.
      Dim keyEnumerator As IEnumerator = CustomerGridView.DataKeys.GetEnumerator()

      ' Iterate though the enumerator and display the primary key
      ' value of each record displayed.
      While keyEnumerator.MoveNext()
      
        Dim key As DataKey = CType(keyEnumerator.Current,
 DataKey)
        MessageLabel.Text &= key.Value.ToString() & "<br/>"
      
      End While

    Else
    
      MessageLabel.Text = "No DataKey objects."
    
    End If

  End Sub
  
</script>

<html>

  <body>
    <form runat="server">
        
      <h3>DataKeyArray Example</h3>
                       
        <asp:gridview id="CustomerGridView"
          datasourceid="CustomerDataSource"
          autogeneratecolumns="true"
          datakeynames="CustomerID"  
          allowpaging="true"
          runat="server">
            
        </asp:gridview>
        
        <br/>
        
        <asp:label id="MessageLabel"
          forecolor="Red"
          runat="server"/>
            
        <!-- This example uses Microsoft SQL Server and connects
  -->
        <!-- to the Northwind sample database. Use an ASP.NET
     -->
        <!-- expression to retrieve the connection string
 value   -->
        <!-- from the Web.config file.                            -->
        <asp:sqldatasource id="CustomerDataSource"
          selectcommand="Select [CustomerID], [CompanyName], [Address],
 [City], [PostalCode], [Country] From [Customers]"
          connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
 
          runat="server"/>
            
      </form>
  </body>
</html>

<%@ Page language="C#" %>

<script runat="server">

  void CustomerGridView_DataBound(Object sender, EventArgs e)
  {

    // Use the Count property to determine whether the
    // DataKeys collection contains any items.
    if (CustomerGridView.DataKeys.Count > 0)
    {

      MessageLabel.Text = "The primary key of each record displayed are: <br/><br/>";

      // Use the GetEnumerator method to create an enumerator that 
      // contains the DataKey objects for the GridView control.
      IEnumerator keyEnumerator = CustomerGridView.DataKeys.GetEnumerator();

      // Iterate though the enumerator and display the primary key
      // value of each record displayed.
      while (keyEnumerator.MoveNext())
      {
        DataKey key = (DataKey)keyEnumerator.Current;
        MessageLabel.Text += key.Value.ToString() + "<br/>";
      }

    }
    else
    {
      MessageLabel.Text = "No DataKey objects.";
    }

  }
  
</script>

<html>

  <body>
    <form runat="server">
        
      <h3>DataKeyArray Example</h3>
                       
        <asp:gridview id="CustomerGridView"
          datasourceid="CustomerDataSource"
          autogeneratecolumns="true"
          datakeynames="CustomerID"  
          allowpaging="true"
          ondatabound="CustomerGridView_DataBound" 
          runat="server">
            
        </asp:gridview>
        
        <br/>
        
        <asp:label id="MessageLabel"
          forecolor="Red"
          runat="server"/>
            
        <!-- This example uses Microsoft SQL Server and connects  -->
        <!-- to the Northwind sample database. Use an ASP.NET     -->
        <!-- expression to retrieve the connection string value
   -->
        <!-- from the Web.config file.                            -->
        <asp:sqldatasource id="CustomerDataSource"
          selectcommand="Select [CustomerID], [CompanyName], [Address], [City],
 [PostalCode], [Country] From [Customers]"
          connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
 
          runat="server"/>
            
      </form>
  </body>
</html>