ParseChildrenAttribute 类

参考

定义

命名空间:: System.Web.UI

程序集:: System.Web.dll

重要

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定义可在开发 ASP.NET 服务器控件时使用的元数据特性。使用 ParseChildrenAttribute 类指示页分析器应如何处理页上声明的服务器控件标记中嵌套的内容。此类不能被继承。

public ref class ParseChildrenAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Class)]
public sealed class ParseChildrenAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Class)>]
type ParseChildrenAttribute = class
    inherit Attribute

Public NotInheritable Class ParseChildrenAttribute
Inherits Attribute

继承: Object

Attribute
ParseChildrenAttribute

属性: AttributeUsageAttribute

示例

本节中的代码示例包含两个部分。第一个代码示例演示如何设置类的属性 ParseChildrenAttribute 。第二个代码示例演示如何在 ASP.NET 页中使用类。

下面的代码示例演示如何设置 ParseChildrenAttribute 名为 CollectionPropertyControl 的自定义服务器控件的对象。将 ParseChildrenAttribute 属性设置为 ChildrenAsProperties 该属性 true ，并将 DefaultProperty 属性设置为 Employee 类。

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);
      }
   }
}

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


        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

        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
    ' 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
    End Class 
End Namespace

下面的代码示例演示如何在 ASP.NET 页中使用CollectionPropertyControl和Employee类。类的 Employee 实例以声明方式添加。

<%@ 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 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="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>

注解

通过类 ParseChildrenAttribute ，可以通过使用 ParseChildrenAttribute 元数据属性标记服务器控件来指定自定义服务器控件分析逻辑。

使用元数据属性 ParseChildren(true) 标记服务器控件指示分析器将服务器控件中包含的元素解释为属性。在此方案中，属性 ChildrenAsProperties 为 true.

使用元数据属性 ParseChildren(true,"<Default Property>") 标记服务器控件会将 DefaultProperty 属性设置为传递到属性的属性的名称。

使用元数据属性 ParseChildren(false)标记服务器控件（默认值）指示分析器将服务器控件标记中包含的元素解释为将与关联（即控件） ControlBuilder 分析的内容。在此方案中，属性 ChildrenAsProperties 为 false.

有关使用属性的信息，请参阅 “属性”。

构造函数

ParseChildrenAttribute()	初始化 ParseChildrenAttribute 类的新实例。
ParseChildrenAttribute(Boolean)	使用 ChildrenAsProperties 属性初始化 ParseChildrenAttribute 类的新实例，以确定包含在服务器控件内的元素是否被分析为服务器控件的属性。
ParseChildrenAttribute(Boolean, String)	使用 `childrenAsProperties` 和 `defaultProperty` 参数初始化 ParseChildrenAttribute 类的新实例。
ParseChildrenAttribute(Type)	使用 ChildControlType 属性初始化 ParseChildrenAttribute 类的新实例，以确定包含在服务器控件内的哪些元素将被分析为控件。

字段

Default	定义 ParseChildrenAttribute 类的默认值。此字段为只读。
ParseAsChildren	指示包含在服务器控件内的嵌套内容被分析为控件。
ParseAsProperties	指示包含在服务器控件内的嵌套内容被分析为控件的属性。

属性

ChildControlType	获取一个值，该值指示控件的允许的类型。
ChildrenAsProperties	获取或设置一个值，该值指示是否要分析作为属性包含在一个服务器控件中的元素。
DefaultProperty	获取或设置元素被分析为的服务器控件的默认属性。
TypeId	在派生类中实现时，获取此 Attribute 的唯一标识符。 (继承自 Attribute)

方法

Equals(Object)	确定指定对象是否等于当前对象。
GetHashCode()	用作 ParseChildrenAttribute 对象的哈希函数。
GetType()	获取当前实例的 Type。 (继承自 Object)
IsDefaultAttribute()	返回一个值，该值指示 ParseChildrenAttribute 类的当前实例的值是否是派生类的默认值。
Match(Object)	当在派生类中重写时，返回一个指示此实例是否等于指定对象的值。 (继承自 Attribute)
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
ToString()	返回表示当前对象的字符串。 (继承自 Object)

显式接口实现

_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)	将一组名称映射为对应的一组调度标识符。 (继承自 Attribute)
_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)	检索对象的类型信息，然后可以使用该信息获取接口的类型信息。 (继承自 Attribute)
_Attribute.GetTypeInfoCount(UInt32)	检索对象提供的类型信息接口的数量（0 或 1）。 (继承自 Attribute)
_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)	提供对某一对象公开的属性和方法的访问。 (继承自 Attribute)

适用于

通过

ParseChildrenAttribute 类

定义

示例

注解

构造函数

字段

属性

方法

显式接口实现

适用于

另请参阅

其他资源