DetailsView.ItemDeleting DetailsView.ItemDeleting DetailsView.ItemDeleting DetailsView.ItemDeleting Event

Definizione

Si verifica quando viene fatto clic su un pulsante Elimina in un controllo DetailsView, ma prima dell'operazione di eliminazione.Occurs when a Delete button within a DetailsView control is clicked, but before the delete operation.

public:
 event System::Web::UI::WebControls::DetailsViewDeleteEventHandler ^ ItemDeleting;
public event System.Web.UI.WebControls.DetailsViewDeleteEventHandler ItemDeleting;
member this.ItemDeleting : System.Web.UI.WebControls.DetailsViewDeleteEventHandler 
Public Custom Event ItemDeleting As DetailsViewDeleteEventHandler 

Esempi

Nell'esempio di codice riportato di seguito viene illustrato ItemDeleting come utilizzare l'evento per annullare l'operazione di eliminazione se l'utente tenta di eliminare l' DetailsView ultimo elemento dal controllo.The following code example demonstrates how to use the ItemDeleting event to cancel the delete operation if the user attempts to delete the last item from the DetailsView control.


<%@ 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 CustomerDetailView_ItemDeleting(Object sender, DetailsViewDeleteEventArgs e)
  {
    // Cancel the delete operation if the user attempts to delete the last
    // record from the data source.
      if (CustomerDetailView.DataItemCount <= 1)
    {
      e.Cancel = true;
      MessageLabel.Text = "You must keep at least one store.";
    }
    else
    {
      MessageLabel.Text = "";
    }
  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>DetailsView ItemDeleting Example</title>
</head>
<body>
    <form id="Form1" runat="server">
        
      <h3>DetailsView ItemDeleting Example</h3>
                
        <asp:detailsview id="CustomerDetailView"
          datasourceid="DetailsViewSource"
          datakeynames="CustomerID"
          autogeneratedeletebutton="true"  
          autogeneraterows="true"
          allowpaging="true"
          onitemdeleting="CustomerDetailView_ItemDeleting" 
          runat="server">
               
          <fieldheaderstyle backcolor="Navy"
            forecolor="White"/>
                    
        </asp:detailsview>
        
        <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="DetailsViewSource" runat="server" 
          ConnectionString=
            "<%$ ConnectionStrings:NorthWindConnectionString%>"
            InsertCommand="INSERT INTO [Customers]([CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country]) VALUES (@CustomerID, @CompanyName, @Address, @City, @PostalCode, @Country)"
            SelectCommand="Select [CustomerID], [CompanyName], 
              [Address], [City], [PostalCode], [Country] 
              From [Customers]"
            DeleteCommand="DELETE FROM [Customers] WHERE [CustomerID] = @CustomerID" >
        </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 CustomerDetailView_ItemDeleting(ByVal sender As Object, ByVal e As DetailsViewDeleteEventArgs)
        ' Cancel the delete operation if the user attempts to delete the last
        ' record from the data source.
        If (CustomerDetailView.DataItemCount <= 1) Then
            e.Cancel = True
            MessageLabel.Text = "You must keep at least one store."
        Else
            MessageLabel.Text = ""
        End If
    End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>DetailsView ItemDeleting Example</title>
</head>
<body>
    <form id="Form1" runat="server">
        
      <h3>DetailsView ItemDeleting Example</h3>
                
        <asp:detailsview id="CustomerDetailView"
          datasourceid="DetailsViewSource"
          datakeynames="CustomerID"
          autogeneratedeletebutton="true"  
          autogeneraterows="true"
          allowpaging="true"
          onitemdeleting="CustomerDetailView_ItemDeleting" 
          runat="server">
               
          <fieldheaderstyle backcolor="Navy"
            forecolor="White"/>
                    
        </asp:detailsview>
        
        <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="DetailsViewSource" runat="server" 
          ConnectionString=
            "<%$ ConnectionStrings:NorthWindConnectionString%>"
            InsertCommand="INSERT INTO [Customers]([CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country]) VALUES (@CustomerID, @CompanyName, @Address, @City, @PostalCode, @Country)"
            SelectCommand="Select [CustomerID], [CompanyName], 
              [Address], [City], [PostalCode], [Country] 
              From [Customers]"
            DeleteCommand="DELETE FROM [Customers] WHERE [CustomerID] = @CustomerID" >
        </asp:SqlDataSource>
    </form>
  </body>
</html>

Commenti

L' ItemDeleting evento viene generato quando si fa clic su un DetailsView pulsante Elimina all'interno del controllo, ma prima dell'operazione di eliminazione.The ItemDeleting event is raised when a Delete button within the DetailsView control is clicked, but before the delete operation. Questo consente di fornire un gestore eventi che esegue una routine personalizzata, ad esempio l'annullamento dell'operazione di eliminazione, ogni volta che si verifica questo evento.This allows you to provide an event handler that performs a custom routine, such as canceling the delete operation, whenever this event occurs.

Un DetailsViewDeleteEventArgs oggetto viene passato al gestore eventi, che consente di determinare l'indice del record da eliminare e di indicare che l'operazione di eliminazione deve essere annullata.A DetailsViewDeleteEventArgs object is passed to the event handler, which allows you to determine the index of the record being deleted and to indicate that the delete operation should be canceled. Per annullare l'operazione di eliminazione, impostare Cancel la proprietà truesu.To cancel the delete operation, set the Cancel property to true. È inoltre possibile modificare le Keys raccolte Values e, se necessario, prima che i valori vengano passati all'origine dati.You can also manipulate the Keys and Values collections, if necessary, before the values are passed to the data source.

Per altre informazioni su come gestire gli eventi, vedere la gestione e generazione di eventi.For more information about how to handle events, see Handling and Raising Events.

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