EmptyControlCollection(Control) Constructor

Definición

Espacio de nombres:

System.Web.UI

Ensamblado:

System.Web.dll

Inicializa una nueva instancia de la clase EmptyControlCollection.

public:
 EmptyControlCollection(System::Web::UI::Control ^ owner);

public EmptyControlCollection (System.Web.UI.Control owner);

new System.Web.UI.EmptyControlCollection : System.Web.UI.Control -> System.Web.UI.EmptyControlCollection

Public Sub New (owner As Control)

Parámetros

owner

Control

Control que es el propietario de esta colección y su colección de controles secundarios.

Ejemplos

En el ejemplo de código siguiente se intenta rellenar un control con controles secundarios, lo que provoca una excepción. Esto se debe a que el control de contenedor no permite controles secundarios. A continuación se muestra la línea de comandos que se usa para compilar el ejecutable.

vbc /r:System.dll /r:System.Web.dll /t:library  
       /out:myWebAppPath/bin/vb_myEmptyControlCollection.dll  
       myEmptyControlCollection.vb  

csc /t:library /out:myWebAppPath/bin/cs_myEmptyControlCollection.dll  
    myEmptyControlCollection.cs  

/* File name: emptyControlCollection.cs. */

using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;

namespace CustomControls
{

  // Defines a simple custom control.
  public class MyCS_EmptyControl : Control
  {
    [System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name="FullTrust")] 
    protected override ControlCollection CreateControlCollection() 
    /*
     * Function Name: CreateControlCollection.
     * Denies the creation of any child control by creating an empty collection.
     * Generates an exception if an attempt to create a child control is made.
     */
     {
       return new EmptyControlCollection(this);
     }
     
     [System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name="FullTrust")] 
     protected override void CreateChildControls()
     /*
      * Function Name: CreateChildControls.
      * Populates the child control collection (Controls). 
      * Note: This function will cause an exception because the control does not allow 
      * child controls.
      */
      {
        // Create a literal control to contain the header and add it to the collection.
        LiteralControl text;
        text = new LiteralControl("<h5>Composite Controls</h5>");
        Controls.Add(text);
      }
   }
}

' File name: emptyControlCollection.vb.

Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Collections


Namespace CustomControls 

  Public Class MyVB_EmptyControl 
    Inherits Control
    
    <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
    Protected Overrides Function CreateControlCollection() As ControlCollection
    ' Function Name: CreateControlCollection.
    ' Denies the creation of any child control by creating an empty collection.
    ' Generates an exception if an attempt to create a child control is made.
      Return New EmptyControlCollection(Me)
    End Function 
    
    <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _  
    Protected Overrides Sub CreateChildControls()
    ' Sub Name: CreateChildControls.
    ' Populates the child control collection (Controls). 
    ' Note: This function will cause an exception because the control does not allow 
    ' child controls.
      Dim text As LiteralControl
      text = New LiteralControl("<h5>Composite Controls</h5>")
      Controls.Add(text)
    End Sub 
  End Class 

End Namespace

En el ejemplo de código siguiente se usa el control personalizado vacío definido anteriormente. Al ejecutar este ejemplo, obtendrá una excepción. Observe que los valores que se muestran en la Register directiva reflejan la línea de comandos anterior.

<%@ Register TagPrefix="custom" Assembly="vb_myEmptyControlCollection" Namespace="CustomControls" %>  
 <html>  
  <body>  
  <h1>Using an Empty Control</h1>  
  <custom:MyVB_EmptyControl id="vbEmptyControlId" runat="server"/>  
  </body>  
 </html>  

<%@ Register TagPrefix="custom" Assembly="cs_myEmptyControlCollection" Namespace="CustomControls" %>  
 <html>  
  <body>  
  <h1>Using an Empty Control </h1>  
  <custom:MyCS_EmptyControl id="csEmptyControlId" runat="server"/>  
  </body>  
 </html>