EmptyControlCollection(Control) 构造函数
定义
重要
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初始化 EmptyControlCollection 类的新实例。
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)参数
示例
下面的代码示例尝试使用子控件填充控件，导致异常。 这是因为容器控件不允许子控件。 下面是用于生成可执行文件的命令行。
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
下面的代码示例使用上面定义的空自定义控件。 运行此示例时，将收到异常。 请注意， 指令中显示的 Register 值反映了上一个命令行。
<%@ 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>
