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DropDownList.CreateControlCollection Método

  • Referencia

Definición

Espacio de nombres:
System.Web.UI.WebControls
Ensamblado:
System.Web.dll

Crea una colección para almacenar controles secundarios.

protected:
 override System::Web::UI::ControlCollection ^ CreateControlCollection();
protected override System.Web.UI.ControlCollection CreateControlCollection ();
override this.CreateControlCollection : unit -> System.Web.UI.ControlCollection
Protected Overrides Function CreateControlCollection () As ControlCollection

Devoluciones

ControlCollection

Siempre devuelve un objeto EmptyControlCollection.

Ejemplos

En el ejemplo de código siguiente se muestra cómo invalidar el CreateControlCollection método en un control de servidor personalizado para que siempre devuelva una nueva instancia de la EmptyControlCollection clase para el DropDownList control . Para obtener información sobre el uso de controles de servidor personalizados, vea Walkthrough: Developing and Using a Custom Web Server Control.

<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>Custom DropDownList - CreateControlCollection - C# Example</title>
    <script runat="server">
      private void Page_Load(object sender, System.EventArgs e)
      {
          DropDownList1.Items.Add(new ListItem("Item1", "Item1"));
          DropDownList1.Items.Add(new ListItem("Item2", "Item2"));
          DropDownList1.Items.Add(new ListItem("Item2", "Item2"));
      }
    </script>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">
      <h3>Custom DropDownList - CreateControlCollection - C# Example</h3>

      <aspSample:CustomDropDownListCreateControlCollection
        id="DropDownList1"
        runat="server" />

    </form>
  </body>
</html>

<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB.Controls" Assembly="Samples.AspNet.VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
        <title>Custom DropDownList - CreateControlCollection - VB.NET Example</title>
        <script runat="server">
            Sub Page_Load(sender As Object, e As EventArgs)
                DropDownList1.Items.Add(New ListItem("Item1", "Item1"))
                DropDownList1.Items.Add(New ListItem("Item2", "Item2"))
                DropDownList1.Items.Add(New ListItem("Item2", "Item2"))
            End Sub
        </script>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom DropDownList - CreateControlCollection - VB.NET Example</h3>
            <aspSample:CustomDropDownListCreateControlCollection id="DropDownList1" runat="server" />
        </form>
    </body>
</html>

using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
{
    [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
    public sealed class CustomDropDownListCreateControlCollection : System.Web.UI.WebControls.DropDownList
    {
        protected override System.Web.UI.ControlCollection CreateControlCollection()
        {
            // Return a new empty ControlCollection
            return new System.Web.UI.EmptyControlCollection(this);
        }
    }
}

Imports System.Web
Imports System.Security.Permissions

Namespace Samples.AspNet.VB.Controls
    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public NotInheritable Class CustomDropDownListCreateControlCollection
        Inherits System.Web.UI.WebControls.DropDownList

        Protected Overrides Function CreateControlCollection() As System.Web.UI.ControlCollection

            ' Return a new EmptyControlCollection
            Return New System.Web.UI.EmptyControlCollection(Me)
        End Function
    End Class
End Namespace

Se aplica a