ListView.ItemCanceling Evento

Definizione

Si verifica quando viene richiesta un'operazione di annullamento, ma prima che il controllo ListView annulli l'operazione di inserimento o modifica.

public:
 event EventHandler<System::Web::UI::WebControls::ListViewCancelEventArgs ^> ^ ItemCanceling;
public event EventHandler<System.Web.UI.WebControls.ListViewCancelEventArgs> ItemCanceling;
member this.ItemCanceling : EventHandler<System.Web.UI.WebControls.ListViewCancelEventArgs> 
Public Custom Event ItemCanceling As EventHandler(Of ListViewCancelEventArgs) 

Tipo evento

Esempio

Nell'esempio seguente viene illustrato come creare un ItemCanceling gestore eventi.

Importante

Questo esempio contiene caselle di testo che accettano l'input utente, ovvero una potenziale minaccia di sicurezza. Per impostazione predefinita, le pagine Web ASP.NET verificano che l'input dell'utente non includa script o elementi HTML. Per altre informazioni, vedere Cenni preliminari sugli attacchi tramite script.

<%@ 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>
  protected void ContactsListView_ItemCanceling(object sender, ListViewCancelEventArgs e)
  {
    //Check the operation that raised the event
    if (e.CancelMode == ListViewCancelMode.CancelingEdit)
    {
      // The update operation was canceled. Display the 
      // primary key of the item.
      Message.Text = "Update for the ContactID " + 
        ContactsListView.DataKeys[e.ItemIndex].Value.ToString()  + " canceled.";
    }
    else
    {
      Message.Text = "Insert operation canceled."; 
    }
  }
  // </Snippet2>

  protected void ContactsListView_PagePropertiesChanging(object sender, 
    PagePropertiesChangingEventArgs e)
  {
    // Clears the edit index selection when paging.
    ContactsListView.EditIndex = -1;
  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head id="Head1" runat="server">
    <title>ListView ItemCanceling Example</title>
  </head>
  <body>
    <form id="form1" runat="server">
        
      <h3>ListView ItemCanceling Example</h3>
      
      <asp:Label ID="Message"
        ForeColor="Red"          
        runat="server"/>
      <br/>
                 
      <asp:ListView ID="ContactsListView" 
        DataSourceID="ContactsDataSource" 
        DataKeyNames="ContactID"
        ConvertEmptyStringToNull="true"
        InsertItemPosition="LastItem"
        runat="server" 
        OnItemCanceling="ContactsListView_ItemCanceling" 
        OnPagePropertiesChanging="ContactsListView_PagePropertiesChanging" >
        <LayoutTemplate>
          <table cellpadding="2" width="680px" border="1" runat="server" id="tblContacts">
            <tr runat="server">
              <th runat="server">&nbsp;</th>
              <th runat="server">ID</th>
              <th runat="server">First Name</th>
              <th runat="server">Last Name</th>
              <th runat="server">Email Address</th>
            </tr>
            <tr runat="server" id="itemPlaceholder" />
          </table>
          <asp:DataPager runat="server" ID="ContactsDataPager" 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="EditButton" runat="server" Text="Edit" CommandName="Edit" /><br />
            </td>
            <td valign="top">
              <asp:Label ID="Label1" runat="server" Text='<%#Eval("ContactID") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="FirstNameLabel" runat="server" Text='<%#Eval("FirstName") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="LastNameLabel" runat="server" Text='<%#Eval("LastName") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="EmailAddressLabel" runat="server" Text='<%#Eval("EmailAddress") %>' />
              &nbsp;
            </td>
          </tr>
        </ItemTemplate>
        <EditItemTemplate>
          <tr style="background-color: #ADD8E6">
            <td valign="top">
              <asp:LinkButton ID="UpdateButton" runat="server" CommandName="Update" Text="Update" /><br />
              <asp:LinkButton ID="CancelEditButton" runat="server" CommandName="Cancel" Text="Cancel" />
            </td>
            <td>
              <asp:Label ID="Label1" runat="server" Text='<%#Eval("ContactID") %>' />
            </td>
            <td>
              <asp:TextBox ID="FirstNameTextBox" runat="server" 
                Text='<%#Bind("FirstName") %>' MaxLength="50" /><br />
            </td>
            <td>
              <asp:TextBox ID="LastNameTextBox" runat="server" 
                Text='<%#Bind("LastName") %>' MaxLength="50" /><br />
            </td>
            <td>
              <asp:TextBox ID="EmailAddressTextBox" runat="server" 
                Text='<%#Bind("EmailAddress") %>' MaxLength="50" /><br />
            </td>
          </tr>
        </EditItemTemplate>
        <InsertItemTemplate>
          <tr style="background-color:#90EE90">
            <td colspan="2">
              <asp:LinkButton ID="InsertButton" runat="server" CommandName="Insert" Text="Insert" /><br />
              <asp:LinkButton ID="CancelInsertButton" runat="server" CommandName="Cancel" Text="Cancel" />
            </td>              
            <td>
              <asp:TextBox ID="FirstNameITextBox" runat="server" 
                Text='<%#Bind("FirstName") %>' MaxLength="50" />
            </td>
            <td>
              <asp:TextBox ID="LastNameITextBox" runat="server" 
                Text='<%#Bind("LastName") %>' MaxLength="50" />
            </td>
            <td>
              <asp:TextBox ID="EmailAddressITextBox" runat="server" 
                Text='<%#Bind("EmailAddress") %>' MaxLength="50" />
           </td>
          </tr>
        </InsertItemTemplate>
      </asp:ListView>

      <!-- This example uses Microsoft SQL Server and connects      -->
      <!-- to the AdventureWorks sample database. Use an ASP.NET    -->
      <!-- expression to retrieve the connection string value       -->
      <!-- from the Web.config file.                                -->
      <asp:SqlDataSource ID="ContactsDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
        SelectCommand="SELECT [ContactID], [FirstName], [LastName], [EmailAddress] FROM Person.Contact"
        InsertCommand="INSERT INTO Person.Contact
                         ([FirstName], [LastName], [EmailAddress], [PasswordHash], [PasswordSalt]) 
                         Values(@FirstName, @LastName, @EmailAddress, '', '')"
        UpdateCommand="UPDATE Person.Contact
                         SET FirstName = @FirstName, LastName = @LastName,
                         EmailAddress = @EmailAddress
                         WHERE ContactID = @ContactID">
      </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>
  Protected Sub ContactsListView_ItemCanceling(ByVal sender As Object, _
                                               ByVal e As ListViewCancelEventArgs)
    'Check the operation that raised the event
    If (e.CancelMode = ListViewCancelMode.CancelingEdit) Then
      ' The update operation was canceled. Display the 
      ' primary key of the item.
      Message.Text = "Update for the ContactID " & _
        ContactsListView.DataKeys(e.ItemIndex).Value.ToString() & " canceled."
    Else
      Message.Text = "Insert operation canceled."
    End If

  End Sub
  ' </Snippet2>
  
  Protected Sub ContactsListView_PagePropertiesChanging(ByVal sender As Object, _
                                               ByVal e As PagePropertiesChangingEventArgs)
    ' Clears the edit index selection when paging.
    ContactsListView.EditIndex = -1
  End Sub
    
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head id="Head1" runat="server">
    <title>ListView ItemCanceling Example</title>
  </head>
  <body>
    <form id="form1" runat="server">
        
      <h3>ListView ItemCanceling Example</h3>
      
      <asp:Label ID="Message"
        ForeColor="Red"          
        runat="server"/>
      <br/>
                 
      <asp:ListView ID="ContactsListView" 
        DataSourceID="ContactsDataSource" 
        DataKeyNames="ContactID"
        ConvertEmptyStringToNull="true"
        InsertItemPosition="LastItem"
        runat="server" 
        OnItemCanceling="ContactsListView_ItemCanceling" 
        OnPagePropertiesChanging="ContactsListView_PagePropertiesChanging" >
        <LayoutTemplate>
          <table cellpadding="2" width="680px" border="1" runat="server" id="tblContacts">
            <tr runat="server">
              <th runat="server">&nbsp;</th>
              <th runat="server">ID</th>
              <th runat="server">First Name</th>
              <th runat="server">Last Name</th>
              <th runat="server">Email Address</th>
            </tr>
            <tr runat="server" id="itemPlaceholder" />
          </table>
          <asp:DataPager runat="server" ID="ContactsDataPager" 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="EditButton" runat="server" Text="Edit" CommandName="Edit" /><br />
            </td>
            <td valign="top">
              <asp:Label ID="Label1" runat="server" Text='<%#Eval("ContactID") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="FirstNameLabel" runat="server" Text='<%#Eval("FirstName") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="LastNameLabel" runat="server" Text='<%#Eval("LastName") %>' />
            </td>
            <td valign="top">
              <asp:Label ID="EmailAddressLabel" runat="server" Text='<%#Eval("EmailAddress") %>' />
              &nbsp;
            </td>
          </tr>
        </ItemTemplate>
        <EditItemTemplate>
          <tr style="background-color: #ADD8E6">
            <td valign="top">
              <asp:LinkButton ID="UpdateButton" runat="server" CommandName="Update" Text="Update" /><br />
              <asp:LinkButton ID="CancelEditButton" runat="server" CommandName="Cancel" Text="Cancel" />
            </td>
            <td>
              <asp:Label ID="Label1" runat="server" Text='<%#Eval("ContactID") %>' />
            </td>
            <td>
              <asp:TextBox ID="FirstNameTextBox" runat="server" 
                Text='<%#Bind("FirstName") %>' MaxLength="50" /><br />
            </td>
            <td>
              <asp:TextBox ID="LastNameTextBox" runat="server" 
                Text='<%#Bind("LastName") %>' MaxLength="50" /><br />
            </td>
            <td>
              <asp:TextBox ID="EmailAddressTextBox" runat="server" 
                Text='<%#Bind("EmailAddress") %>' MaxLength="50" /><br />
            </td>
          </tr>
        </EditItemTemplate>
        <InsertItemTemplate>
          <tr style="background-color:#90EE90">
            <td colspan="2">
              <asp:LinkButton ID="InsertButton" runat="server" CommandName="Insert" Text="Insert" /><br />
              <asp:LinkButton ID="CancelInsertButton" runat="server" CommandName="Cancel" Text="Cancel" />
            </td>              
            <td>
              <asp:TextBox ID="FirstNameITextBox" runat="server" 
                Text='<%#Bind("FirstName") %>' MaxLength="50" />
            </td>
            <td>
              <asp:TextBox ID="LastNameITextBox" runat="server" 
                Text='<%#Bind("LastName") %>' MaxLength="50" />
            </td>
            <td>
              <asp:TextBox ID="EmailAddressITextBox" runat="server" 
                Text='<%#Bind("EmailAddress") %>' MaxLength="50" />
           </td>
          </tr>
        </InsertItemTemplate>
      </asp:ListView>

      <!-- This example uses Microsoft SQL Server and connects      -->
      <!-- to the AdventureWorks sample database. Use an ASP.NET    -->
      <!-- expression to retrieve the connection string value       -->
      <!-- from the Web.config file.                                -->
      <asp:SqlDataSource ID="ContactsDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
        SelectCommand="SELECT [ContactID], [FirstName], [LastName], [EmailAddress] FROM Person.Contact"
        InsertCommand="INSERT INTO Person.Contact
                         ([FirstName], [LastName], [EmailAddress], [PasswordHash], [PasswordSalt]) 
                         Values(@FirstName, @LastName, @EmailAddress, '', '')"
        UpdateCommand="UPDATE Person.Contact
                         SET FirstName = @FirstName, LastName = @LastName,
                         EmailAddress = @EmailAddress
                         WHERE ContactID = @ContactID">
      </asp:SqlDataSource>
      
    </form>
  </body>
</html>

Commenti

Il ListView controllo genera l'evento ItemCanceling quando viene fatto clic su un pulsante Annulla nel InsertItemTemplate modello o EditItemTemplate , ma prima che il ListView controllo annulla l'operazione di inserimento o modifica. Un pulsante Annulla è un controllo pulsante la cui CommandName proprietà è impostata su "Annulla". Ciò consente di eseguire una routine personalizzata ogni volta che si verifica questo evento, ad esempio arrestare l'operazione di annullamento se l'elemento verrà inserito in uno stato indesiderato.

Un ListViewCancelEventArgs oggetto viene passato al gestore eventi, che consente di determinare l'indice dell'elemento. Consente inoltre di indicare che l'operazione di annullamento deve essere arrestata. Per arrestare l'operazione, impostare la Cancel proprietà dell'oggetto ListViewCancelEventArgs su true.

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

Si applica a

Vedi anche