ListView.SelectedIndexChanging Evento

Definizione

Spazio dei nomi:: System.Web.UI.WebControls

Assembly:: System.Web.Extensions.dll

Importante

Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.

Si verifica quando si fa clic sul pulsante Select di un elemento, ma prima che il ListView controllo gestisca l'operazione di selezione.

public:
 event EventHandler<System::Web::UI::WebControls::ListViewSelectEventArgs ^> ^ SelectedIndexChanging;

public event EventHandler<System.Web.UI.WebControls.ListViewSelectEventArgs> SelectedIndexChanging;

member this.SelectedIndexChanging : EventHandler<System.Web.UI.WebControls.ListViewSelectEventArgs>

Public Custom Event SelectedIndexChanging As EventHandler(Of ListViewSelectEventArgs)

Tipo evento

EventHandler<ListViewSelectEventArgs>

Esempio

Nell'esempio seguente viene illustrato come creare un gestore eventi per l'evento SelectedIndexChanging .

<%@ Page language="C#" %>
    
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    
<script runat="server">

  void Page_Load()
  {
    Message.Text = String.Empty;
  }
      
  //<Snippet2>
  void ProductsListView_SelectedIndexChanging(Object sender, ListViewSelectEventArgs e)
  {
    ListViewItem item = (ListViewItem)ProductsListView.Items[e.NewSelectedIndex];
    Label l = (Label)item.FindControl("DiscontinuedDateLabel");

    if (String.IsNullOrEmpty(l.Text))
    {
      return;
    }

    DateTime discontinued = DateTime.Parse(l.Text);
    if (discontinued < DateTime.Now)
    {
      Message.Text = "You cannot select a discontinued item.";
      e.Cancel = true;
    }
  }
  //</Snippet2>

  protected void ProductsListView_PagePropertiesChanging(object sender, PagePropertiesChangingEventArgs e)
  {
    // Clear selection.
    ProductsListView.SelectedIndex = -1;
  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head id="Head1" runat="server">
    <title>ListView.SelectedIndexChanging Example</title>
  </head>
  <body>
    <form id="form1" runat="server">
        
      <h3>ListView.SelectedIndexChanging Example</h3>

      <asp:Label ID="Message"
        ForeColor="Red"          
        runat="server"/>
      <br/>
     
      <asp:ListView ID="ProductsListView" 
        DataSourceID="ProductsDataSource" 
        DataKeyNames="ProductID"
        OnSelectedIndexChanging="ProductsListView_SelectedIndexChanging"         
        OnPagePropertiesChanging="ProductsListView_PagePropertiesChanging"
        runat="server" >
        <LayoutTemplate>
          <table cellpadding="2" runat="server" id="tblProducts" width="640px">
            <tr runat="server" id="itemPlaceholder" />
          </table>
          <asp:DataPager runat="server" ID="ProductsDataPager" PageSize="12">
            <Fields>
              <asp:NextPreviousPagerField 
                ShowFirstPageButton="true" ShowLastPageButton="true"
                FirstPageText="|&lt;&lt; " LastPageText=" &gt;&gt;|"
                NextPageText=" &gt; " PreviousPageText=" &lt; " />
            </Fields>
          </asp:DataPager>
        </LayoutTemplate>
        <ItemTemplate>
          <tr runat="server">
            <td valign="top">
              <asp:LinkButton ID="SelectButton" runat="server" Text="..." CommandName="Select" />
            </td>
            <td valign="top">
              <asp:Label ID="NameLabel" runat="server" Text='<%#Eval("Name") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="ProductNumberLabel" runat="server" Text='<%#Eval("ProductNumber") %>' />
            </td>
            <td>
              <asp:Label ID="DiscontinuedDateLabel" runat="server" Text='<%#Eval("DiscontinuedDate", "{0:d}") %>' />
            </td>
          </tr>
        </ItemTemplate>
        <SelectedItemTemplate>
          <tr runat="server" style="background-color:#ADD8E6">
            <td>&nbsp;</td>
            <td valign="top">
              <asp:Label ID="NameLabel" runat="server" Text='<%#Eval("Name") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="ProductNumberLabel" runat="server" Text='<%#Eval("ProductNumber") %>' />
            </td>
            <td>
              <asp:Label ID="DiscontinuedDateLabel" runat="server" Text='<%#Eval("DiscontinuedDate", "{0:d}") %>' />
            </td>
          </tr>
        </SelectedItemTemplate>
      </asp:ListView>
            
      <asp:SqlDataSource ID="ProductsDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
        SelectCommand="SELECT [ProductID], [Name], [ProductNumber], [DiscontinuedDate] 
          FROM Production.Product"
        UpdateCommand="UPDATE Production.Product
           SET Name = @Name, ProductNumber = @ProductNumber, DiscontinuedDate = @DiscontinuedDate
           WHERE ProductID = @ProductID">
      </asp:SqlDataSource>
      
    </form>
  </body>
</html>

<%@ Page language="VB" %>
    
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    
<script runat="server">
  
  Sub Page_Load()
    Message.Text = String.Empty
  End Sub
  
  '<Snippet2>
  Sub ProductsListView_SelectedIndexChanging(ByVal sender As Object, ByVal e As ListViewSelectEventArgs)

    Dim item As ListViewItem = CType(ProductsListView.Items(e.NewSelectedIndex), ListViewItem)  
    Dim l As Label = CType(item.FindControl("DiscontinuedDateLabel"), Label)

    If String.IsNullOrEmpty(l.Text) Then
      Return
    End If

    Dim discontinued As DateTime = DateTime.Parse(l.Text)
    If discontinued < DateTime.Now Then      
      Message.Text = "You cannot select a discontinued item."
      e.Cancel = True
    End If
  End Sub
  '</Snippet2>
  
  Protected Sub ProductsListView_PagePropertiesChanging(ByVal sender As Object, _
                                               ByVal e As PagePropertiesChangingEventArgs)
    ' Clears the selection.
    ProductsListView.SelectedIndex = -1
  End Sub
  
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head id="Head1" runat="server">
    <title>ListView.SelectedIndexChanging Example</title>
  </head>
  <body>
    <form id="form1" runat="server">
        
      <h3>ListView.SelectedIndexChanging Example</h3>

      <asp:Label ID="Message"
        ForeColor="Red"          
        runat="server"/>
      <br/>
     
      <asp:ListView ID="ProductsListView" 
        DataSourceID="ProductsDataSource" 
        DataKeyNames="ProductID"
        OnSelectedIndexChanging="ProductsListView_SelectedIndexChanging" 
        OnPagePropertiesChanging="ProductsListView_PagePropertiesChanging"
        runat="server">
        <LayoutTemplate>
          <table cellpadding="2" runat="server" id="tblProducts" width="640px">
            <tr runat="server" id="itemPlaceholder" />
          </table>
          <asp:DataPager runat="server" ID="ProductsDataPager" PageSize="12">
            <Fields>
              <asp:NextPreviousPagerField 
                ShowFirstPageButton="true" ShowLastPageButton="true"
                FirstPageText="|&lt;&lt; " LastPageText=" &gt;&gt;|"
                NextPageText=" &gt; " PreviousPageText=" &lt; " />
            </Fields>
          </asp:DataPager>
        </LayoutTemplate>
        <ItemTemplate>
          <tr runat="server">
            <td valign="top">
              <asp:LinkButton ID="SelectButton" runat="server" Text="..." CommandName="Select" />
            </td>
            <td valign="top">
              <asp:Label ID="NameLabel" runat="server" Text='<%#Eval("Name") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="ProductNumberLabel" runat="server" Text='<%#Eval("ProductNumber") %>' />
            </td>
            <td>
              <asp:Label ID="DiscontinuedDateLabel" runat="server" Text='<%#Eval("DiscontinuedDate", "{0:d}") %>' />
            </td>
          </tr>
        </ItemTemplate>
        <SelectedItemTemplate>
          <tr runat="server" style="background-color:#ADD8E6">
            <td>&nbsp;</td>
            <td valign="top">
              <asp:Label ID="NameLabel" runat="server" Text='<%#Eval("Name") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="ProductNumberLabel" runat="server" Text='<%#Eval("ProductNumber") %>' />
            </td>
            <td>
              <asp:Label ID="DiscontinuedDateLabel" runat="server" Text='<%#Eval("DiscontinuedDate", "{0:d}") %>' />
            </td>
          </tr>
        </SelectedItemTemplate>
      </asp:ListView>
            
      <asp:SqlDataSource ID="ProductsDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
        SelectCommand="SELECT [ProductID], [Name], [ProductNumber], [DiscontinuedDate] 
          FROM Production.Product"
        UpdateCommand="UPDATE Production.Product
           SET Name = @Name, ProductNumber = @ProductNumber, DiscontinuedDate = @DiscontinuedDate
           WHERE ProductID = @ProductID">
      </asp:SqlDataSource>
      
    </form>
  </body>
</html>

Commenti

L'evento SelectedIndexChanging viene generato quando si fa clic sul pulsante Select di un elemento, ma prima che il ListView controllo gestisca l'operazione di selezione. Un pulsante Seleziona è un controllo pulsante la cui CommandName proprietà è impostata su "Seleziona". In questo modo è possibile eseguire una routine personalizzata ogni volta che si verifica questo evento, ad esempio l'annullamento dell'operazione di selezione.

Annotazioni

Questo evento non viene generato quando si imposta la SelectedIndex proprietà a livello di codice.

Un ListViewSelectEventArgs oggetto viene passato al gestore eventi, che consente di determinare l'indice dell'elemento selezionato dall'utente. Consente inoltre di indicare che l'operazione di selezione deve essere annullata. Per annullare l'operazione di selezione, impostare la Cancel proprietà dell'oggetto ListViewSelectEventArgs su true.

Per altre informazioni su come gestire gli eventi, vedere Gestione e generazione di eventi.

Si applica a

Vedi anche

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