ParseChildrenAttribute-Klasse
Definiert ein Metadatenattribut, das bei der Entwicklung von ASP.NET-Serversteuerelementen verwendet werden kann. Mit der ParseChildrenAttribute-Klasse können Sie angeben, wie der Seitenparser mit Inhalten verfahren soll, die in einem auf einer Seite deklarierten Serversteuerelementtag geschachtelt sind. Diese Klasse kann nicht geerbt werden.
Namespace: System.Web.UI
Assembly: System.Web (in system.web.dll)
Syntax
'Declaration
<AttributeUsageAttribute(AttributeTargets.Class)> _
Public NotInheritable Class ParseChildrenAttribute
Inherits Attribute
'Usage
Dim instance As ParseChildrenAttribute
[AttributeUsageAttribute(AttributeTargets.Class)]
public sealed class ParseChildrenAttribute : Attribute
[AttributeUsageAttribute(AttributeTargets::Class)]
public ref class ParseChildrenAttribute sealed : public Attribute
/** @attribute AttributeUsageAttribute(AttributeTargets.Class) */
public final class ParseChildrenAttribute extends Attribute
AttributeUsageAttribute(AttributeTargets.Class)
public final class ParseChildrenAttribute extends Attribute
Hinweise
Mit der ParseChildrenAttribute-Klasse können Benutzer eine Analyselogik für ein benutzerdefiniertes Serversteuerelement angeben, indem sie das Serversteuerelement mit dem ParseChildrenAttribute-Metadatenattribut markieren.
Durch Markieren des Serversteuerelements mit dem Metadatenattribut ParseChildren(true) wird der Parser angewiesen, die in den Serversteuerelementtags enthaltenen Elemente als Eigenschaften zu interpretieren. In diesem Szenario ist die ChildrenAsProperties-Eigenschaft true.
Durch Markieren des Serversteuerelements mit dem Metadatenattribut ParseChildren(true,"<Default Property>") wird die DefaultProperty-Eigenschaft auf den Namen der Eigenschaft festgelegt, die an das Attribut übergeben wird.
Durch Markieren des Serversteuerelements mit dem Metadatenattribut ParseChildren(false) (Standardwert) wird der Parser angewiesen, die in den Steuerelementtags enthaltenen Elemente als Inhalte zu interpretieren, die mit einem zugeordneten ControlBuilder analysiert werden, und sie somit als Steuerelemente zu betrachten. In diesem Szenario ist die ChildrenAsProperties-Eigenschaft false.
Weitere Informationen über das Verwenden von Attributen finden Sie unter Erweitern von Metadaten mithilfe von Attributen.
| Thema | Position |
|---|---|
| Exemplarische Vorgehensweise: Entwickeln und Verwenden eines benutzerdefinierten Serversteuerelements | Entwickeln von ASP.NET-Steuerelementen |
| Exemplarische Vorgehensweise: Entwickeln und Verwenden eines benutzerdefinierten Serversteuerelements | Erstellen von Anwendungen mit Visual Web Developer |
Beispiel
Das Codebeispiel in diesem Abschnitt besteht aus zwei Teilen. Im ersten Teil wird das Festlegen von Eigenschaften für die ParseChildrenAttribute-Klasse veranschaulicht. Im zweiten Teil wird die Verwendung von Klassen in einer ASP.NET-Seite veranschaulicht.
Im folgenden Codebeispiel wird veranschaulicht, wie das ParseChildrenAttribute-Objekt eines benutzerdefinierten Serversteuerelements mit dem Namen CollectionPropertyControl festgelegt wird. Mithilfe von ParseChildrenAttribute wird die ChildrenAsProperties-Eigenschaft auf true festgelegt, und die DefaultProperty-Eigenschaft wird auf die Employee-Klasse festgelegt.
Imports System
Imports System.Collections
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Security.Permissions
Namespace Samples.AspNet.VB.Controls
' The child element class.
<AspNetHostingPermission(SecurityAction.Demand, _
Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class Employee
Private _name As String
Private _title As String
Private _alias As String
Public Sub New()
Me.New("", "", "")
End Sub 'New
Public Sub New(ByVal name As String, ByVal title As String, ByVal employeeAlias As String)
Me._name = name
Me._title = title
Me._alias = employeeAlias
End Sub 'New
Public Property Name() As String
Get
Return _name
End Get
Set(ByVal value As String)
_name = Value
End Set
End Property
Public Property Title() As String
Get
Return _title
End Get
Set(ByVal value As String)
_title = Value
End Set
End Property
Public Property [Alias]() As String
Get
Return _alias
End Get
Set(ByVal value As String)
_alias = Value
End Set
End Property
End Class 'Employee
' Use the ParseChildren attribute to set the ChildrenAsProperties
' and DefaultProperty properties. Using this constructor, the
' control parses all child controls as properties and must define
' a public property named Employees, which it declares as
' an ArrayList. Nested (child) elements must correspond to
' child elements of the Employees property or to other
' properties of the control.
<ParseChildren(True, "Employees")> _
<AspNetHostingPermission(SecurityAction.Demand, _
Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CollectionPropertyControl
Inherits Control
Private _header As String
Private _employees As New ArrayList()
Public Property Header() As String
Get
Return _header
End Get
Set(ByVal value As String)
_header = Value
End Set
End Property
Public ReadOnly Property Employees() As ArrayList
Get
Return _employees
End Get
End Property
' Override the CreateChildControls method to
' add child controls to the Employees property when this
' custom control is requested from a page.
Protected Overrides Sub CreateChildControls()
Dim label As New Label()
label.Text = Header
label.BackColor = System.Drawing.Color.Beige
label.ForeColor = System.Drawing.Color.Red
Controls.Add(label)
Controls.Add(New LiteralControl("<BR> <BR>"))
Dim table As New Table()
Dim htr As New TableRow()
Dim hcell1 As New TableHeaderCell()
hcell1.Text = "Name"
htr.Cells.Add(hcell1)
Dim hcell2 As New TableHeaderCell()
hcell2.Text = "Title"
htr.Cells.Add(hcell2)
Dim hcell3 As New TableHeaderCell()
hcell3.Text = "Alias"
htr.Cells.Add(hcell3)
table.Rows.Add(htr)
table.BorderWidth = Unit.Pixel(2)
table.BackColor = System.Drawing.Color.Beige
table.ForeColor = System.Drawing.Color.Red
Dim employee As Employee
For Each employee In Employees
Dim tr As New TableRow()
Dim cell1 As New TableCell()
cell1.Text = employee.Name
tr.Cells.Add(cell1)
Dim cell2 As New TableCell()
cell2.Text = employee.Title
tr.Cells.Add(cell2)
Dim cell3 As New TableCell()
cell3.Text = employee.Alias
tr.Cells.Add(cell3)
table.Rows.Add(tr)
Next employee
Controls.Add(table)
End Sub 'CreateChildControls
End Class
End Namespace
using System;
using System.Collections;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Security.Permissions;
namespace Samples.AspNet.CS.Controls
{
// The child element class.
[AspNetHostingPermission(SecurityAction.Demand,
Level=AspNetHostingPermissionLevel.Minimal)]
public sealed class Employee
{
private String name;
private String title;
private String alias;
public Employee():this ("","",""){}
public Employee (String name, String title, String alias)
{
this.name = name;
this.title = title;
this.alias = alias;
}
public String Name
{
get
{
return name;
}
set
{
name = value;
}
}
public String Title
{
get
{
return title;
}
set
{
title = value;
}
}
public String Alias
{
get
{
return alias;
}
set
{
alias = value;
}
}
}
// Use the ParseChildren attribute to set the ChildrenAsProperties
// and DefaultProperty properties. Using this constructor, the
// control parses all child controls as properties and must define
// a public property named Employees, which it declares as
// an ArrayList. Nested (child) elements must correspond to
// child elements of the Employees property or to other
// properties of the control.
[ParseChildren(true, "Employees")]
[AspNetHostingPermission(SecurityAction.Demand,
Level=AspNetHostingPermissionLevel.Minimal)]
public sealed class CollectionPropertyControl : Control
{
private String header;
private ArrayList employees = new ArrayList();
public String Header
{
get
{
return header;
}
set
{
header = value;
}
}
public ArrayList Employees
{
get
{
return employees;
}
}
// Override the CreateChildControls method to
// add child controls to the Employees property when this
// custom control is requested from a page.
protected override void CreateChildControls()
{
Label label = new Label();
label.Text = Header;
label.BackColor = System.Drawing.Color.Beige;
label.ForeColor = System.Drawing.Color.Red;
Controls.Add(label);
Controls.Add(new LiteralControl("<BR> <BR>"));
Table table = new Table();
TableRow htr = new TableRow();
TableHeaderCell hcell1 = new TableHeaderCell();
hcell1.Text = "Name";
htr.Cells.Add(hcell1);
TableHeaderCell hcell2 = new TableHeaderCell();
hcell2.Text = "Title";
htr.Cells.Add(hcell2);
TableHeaderCell hcell3 = new TableHeaderCell();
hcell3.Text = "Alias";
htr.Cells.Add(hcell3);
table.Rows.Add(htr);
table.BorderWidth = 2;
table.BackColor = System.Drawing.Color.Beige;
table.ForeColor = System.Drawing.Color.Red;
foreach (Employee employee in Employees)
{
TableRow tr = new TableRow();
TableCell cell1 = new TableCell();
cell1.Text = employee.Name;
tr.Cells.Add(cell1);
TableCell cell2 = new TableCell();
cell2.Text = employee.Title;
tr.Cells.Add(cell2);
TableCell cell3 = new TableCell();
cell3.Text = employee.Alias;
tr.Cells.Add(cell3);
table.Rows.Add(tr);
}
Controls.Add(table);
}
}
}
package ParseChildrenSamples;
// When compiling this class, name it ParseChildren.dll.
// Create a namespace that defines two classes: one is a custom control
// named Employee, which is created for every instance of a child
// element with its name declared in a page associated with this namespace,
// and the other, named Employees, that contains these child elements.
import System.*;
import System.Collections.*;
import System.Web.*;
import System.Web.UI.*;
import System.Web.UI.WebControls.*;
// The child element class.
public class Employee
{
private String name;
private String title;
private String alias;
public Employee()
{
this("", "", "");
} //Employee
public Employee(String name, String title, String alias)
{
this.name = name;
this.title = title;
this.alias = alias;
} //Employee
/** @property
*/
public String get_Name()
{
return name;
} //get_Name
/** @property
*/
public void set_Name(String value)
{
name = value;
} //set_Name
/** @property
*/
public String get_Title()
{
return title;
} //get_Title
/** @property
*/
public void set_Title(String value)
{
title = value;
} //set_Title
/** @property
*/
public String get_Alias()
{
return alias;
} //get_Alias
/** @property
*/
public void set_Alias(String value)
{
alias = value;
} //set_Alias
} //Employee
// Use the ParseChildren attribute to set the ChildrenAsProperties
// and DefaultProperty properties. Using this constructor, the
// control parses all child controls as properties and must define
// a public property named Employees, which it declares as
// an ArrayList. Nested (child) elements must correspond to
// child elements of the Employees property or to other
// properties of the control.
/** @attribute ParseChildren(true, "Employees")
*/
public class CollectionPropertyControl extends Control
{
private String header;
private ArrayList employees = new ArrayList();
/** @property
*/
public String get_Header()
{
return header;
} //get_Header
/** @property
*/
public void set_Header(String value)
{
header = value;
} //set_Header
/** @property
*/
public ArrayList get_Employees()
{
return employees;
} //get_Employees
// Override the CreateChildControls method to
// add child controls to the Employees property when this
// custom control is requested from a page.
protected void CreateChildControls()
{
Label label = new Label();
label.set_Text(get_Header());
label.set_BackColor(System.Drawing.Color.get_Beige());
label.set_ForeColor(System.Drawing.Color.get_Red());
get_Controls().Add(label);
get_Controls().Add(new LiteralControl("<BR> <BR>"));
Table table = new Table();
TableRow htr = new TableRow();
TableHeaderCell hCell1 = new TableHeaderCell();
hCell1.set_Text("Name");
htr.get_Cells().Add(hCell1);
TableHeaderCell hCell2 = new TableHeaderCell();
hCell2.set_Text("Title");
htr.get_Cells().Add(hCell2);
TableHeaderCell hCell3 = new TableHeaderCell();
hCell3.set_Text("Alias");
htr.get_Cells().Add(hCell3);
table.get_Rows().Add(htr);
table.set_BorderWidth(new Unit(2));
table.set_BackColor(System.Drawing.Color.get_Beige());
table.set_ForeColor(System.Drawing.Color.get_Red());
Employee employee = null;
for (int iCtr = 0; iCtr < get_Employees().get_Count(); iCtr++) {
employee = (Employee)get_Employees().get_Item(iCtr);
TableRow tr = new TableRow();
TableCell cell1 = new TableCell();
cell1.set_Text(employee.get_Name());
tr.get_Cells().Add(cell1);
TableCell cell2 = new TableCell();
cell2.set_Text(employee.get_Title());
tr.get_Cells().Add(cell2);
TableCell cell3 = new TableCell();
cell3.set_Text(employee.get_Alias());
tr.get_Cells().Add(cell3);
table.get_Rows().Add(tr);
}
get_Controls().Add(table);
} //CreateChildControls
} //CollectionPropertyControl
Im folgenden Codebeispiel wird veranschaulicht, wie die CollectionPropertyControl-Klasse und die Employee-Klasse in einer ASP.NET-Seite verwendet werden. Instanzen der Employee-Klasse werden deklarativ hinzugefügt.
<%@ Page Language="VB" %>
<%@ Register TagPrefix="AspSample" Assembly="Samples.AspNet.VB.Controls" Namespace="Samples.AspNet.VB.Controls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
' Verify attribute values.
Dim p As ParseChildrenAttribute = _
Attribute.GetCustomAttribute(GetType(CollectionPropertyControl), _
GetType(ParseChildrenAttribute))
Dim sb As New StringBuilder()
sb.Append("The DefaultProperty property is " & p.DefaultProperty.ToString() & "<br>")
sb.Append("The ChildrenAsProperties property is " & p.ChildrenAsProperties.ToString() & "<br>")
sb.Append("The IsDefaultAttribute method returns " & p.IsDefaultAttribute().ToString())
Message.Text = sb.ToString()
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>PersistChildrenAttribute</title>
</head>
<body>
<form id="Form1" runat="server">
<div>
<asp:Label ID="Message"
runat="server"/>
<AspSample:CollectionPropertyControl id="CollectionPropertyControl1"
runat="server">
<AspSample:Employee Name="Employee 1"
Title="Title 1"
Alias="Alias 1" />
<AspSample:Employee Name="Employee 2"
Title="Title 2"
Alias="Alias 2" />
</AspSample:CollectionPropertyControl>
</div>
</form>
</body>
</html>
<%@ Page Language="C#" Debug="true" %>
<%@ Register TagPrefix="AspSample" Assembly="Samples.AspNet.CS.Controls" Namespace="Samples.AspNet.CS.Controls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void Page_Load(object sender, EventArgs e)
{
// Verify attribute values.
ParseChildrenAttribute p =
(ParseChildrenAttribute)Attribute.GetCustomAttribute(typeof(CollectionPropertyControl),
typeof(ParseChildrenAttribute));
StringBuilder sb = new StringBuilder();
sb.Append("The DefaultProperty property is " + p.DefaultProperty.ToString() + "<br>");
sb.Append("The ChildrenAsProperties property is " + p.ChildrenAsProperties.ToString() + "<br>");
sb.Append("The IsDefaultAttribute method returns " + p.IsDefaultAttribute().ToString());
Message.Text = sb.ToString();
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>ParseChildrenAttribute Example</title>
</head>
<body>
<form runat="server">
<div>
<asp:Label ID="Message"
runat="server"/>
<AspSample:CollectionPropertyControl id="CollectionPropertyControl1"
runat="server">
<AspSample:Employee Name="Employee 1"
Title="Title 1"
Alias="Alias 1" />
<AspSample:Employee Name="Employee 2"
Title="Title 2"
Alias="Alias 2" />
</AspSample:CollectionPropertyControl>
</div>
</form>
</body>
</html>
.NET Framework-Sicherheit
- AspNetHostingPermission für den Betrieb in einer Hostumgebung. Anforderungswert: LinkDemand; Berechtigungswert: Minimal.
Vererbungshierarchie
System.Object
System.Attribute
System.Web.UI.ParseChildrenAttribute
Threadsicherheit
Alle öffentlichen statischen (Shared in Visual Basic) Member dieses Typs sind threadsicher. Bei Instanzmembern ist die Threadsicherheit nicht gewährleistet.
Plattformen
Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
Siehe auch
Referenz
ParseChildrenAttribute-Member
System.Web.UI-Namespace
Attribute
PersistChildrenAttribute