EmptyControlCollection(Control) Construtor
Definição
Importante
Algumas informações se referem a produtos de pré-lançamento que podem ser substancialmente modificados antes do lançamento. A Microsoft não oferece garantias, expressas ou implícitas, das informações aqui fornecidas.
Inicializa uma nova instância da classe 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.EmptyControlCollectionPublic Sub New (owner As Control)Parâmetros
Exemplos
O exemplo de código a seguir tenta preencher um controle com controles filho, causando uma exceção. Isso ocorre porque o controle de contêiner não permite controles filho. A seguir está a linha de comando usada para compilar o executável.
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
O exemplo de código a seguir usa o controle personalizado vazio definido acima. Ao executar este exemplo, você receberá uma exceção. Observe que os valores mostrados na Register diretiva refletem a linha de comando 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>