StateManagedCollection 类
定义
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
为管理 IStateManager 对象的所有强类型集合提供基类。
public ref class StateManagedCollection abstract : System::Collections::IList, System::Web::UI::IStateManagerpublic abstract class StateManagedCollection : System.Collections.IList, System.Web.UI.IStateManagertype StateManagedCollection = class
interface IList
interface ICollection
interface IEnumerable
interface IStateManagerPublic MustInherit Class StateManagedCollection
Implements IList, IStateManager- 继承
-
StateManagedCollection
- 派生
- 实现
示例
下面的代码示例演示如何从 StateManagedCollection 中派生强类型集合类以包含 IStateManager 对象。 在此示例中，CycleCollection派生为包含抽象Cycle类的实例（可以是Bicycle``Tricycle或对象）。 该 Cycle 类实现 IStateManager 接口，因为它将属性的值 CycleColor 存储在视图状态中。
namespace Samples.AspNet.CS.Controls {
using System;
using System.Security.Permissions;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Web;
using System.Web.UI;
//////////////////////////////////////////////////////////////
//
// The strongly typed CycleCollection class is a collection
// that contains Cycle class instances, which implement the
// IStateManager interface.
//
//////////////////////////////////////////////////////////////
[AspNetHostingPermission(SecurityAction.Demand,
Level=AspNetHostingPermissionLevel.Minimal)]
public sealed class CycleCollection : StateManagedCollection {
private static readonly Type[] _typesOfCycles
= new Type[] { typeof(Bicycle), typeof(Tricycle) };
protected override object CreateKnownType(int index) {
switch(index) {
case 0:
return new Bicycle();
case 1:
return new Tricycle();
default:
throw new ArgumentOutOfRangeException("Unknown Type");
}
}
protected override Type[] GetKnownTypes() {
return _typesOfCycles;
}
protected override void SetDirtyObject(object o) {
((Cycle)o).SetDirty();
}
}
//////////////////////////////////////////////////////////////
//
// The abstract Cycle class represents bicycles and tricycles.
//
//////////////////////////////////////////////////////////////
public abstract class Cycle : IStateManager {
protected internal Cycle(int numWheels) : this(numWheels, "Red"){ }
protected internal Cycle(int numWheels, String color) {
numberOfWheels = numWheels;
CycleColor = color;
}
private int numberOfWheels = 0;
public int NumberOfWheels {
get { return numberOfWheels; }
}
public string CycleColor {
get {
object o = ViewState["Color"];
return (null == o) ? String.Empty : o.ToString() ;
}
set {
ViewState["Color"] = value;
}
}
internal void SetDirty() {
ViewState.SetDirty(true);
}
// Because Cycle does not derive from Control, it does not
// have access to an inherited view state StateBag object.
private StateBag viewState;
private StateBag ViewState {
get {
if (viewState == null) {
viewState = new StateBag(false);
if (isTrackingViewState) {
((IStateManager)viewState).TrackViewState();
}
}
return viewState;
}
}
// The IStateManager implementation.
private bool isTrackingViewState;
bool IStateManager.IsTrackingViewState {
get {
return isTrackingViewState;
}
}
void IStateManager.LoadViewState(object savedState) {
object[] cycleState = (object[]) savedState;
// In SaveViewState, an array of one element is created.
// Therefore, if the array passed to LoadViewState has
// more than one element, it is invalid.
if (cycleState.Length != 1) {
throw new ArgumentException("Invalid Cycle View State");
}
// Call LoadViewState on the StateBag object.
((IStateManager)ViewState).LoadViewState(cycleState[0]);
}
// Save the view state by calling the StateBag's SaveViewState
// method.
object IStateManager.SaveViewState() {
object[] cycleState = new object[1];
if (viewState != null) {
cycleState[0] = ((IStateManager)viewState).SaveViewState();
}
return cycleState;
}
// Begin tracking view state. Check the private variable, because
// if the view state has not been accessed or set, then it is not
// being used and there is no reason to store any view state.
void IStateManager.TrackViewState() {
isTrackingViewState = true;
if (viewState != null) {
((IStateManager)viewState).TrackViewState();
}
}
}
public sealed class Bicycle : Cycle {
// Create a red Cycle with two wheels.
public Bicycle() : base(2) {}
}
public sealed class Tricycle : Cycle {
// Create a red Cycle with three wheels.
public Tricycle() : base(3) {}
}
}
Imports System.Security.Permissions
Imports System.Collections
Imports System.ComponentModel
Imports System.Drawing
Imports System.Web
Imports System.Web.UI
Namespace Samples.AspNet.VB.Controls
'////////////////////////////////////////////////////////////
'
' The strongly typed CycleCollection class is a collection
' that contains Cycle class instances, which implement the
' IStateManager interface.
'
'////////////////////////////////////////////////////////////
<AspNetHostingPermission(SecurityAction.Demand, _
Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CycleCollection
Inherits StateManagedCollection
Private Shared _typesOfCycles() As Type = _
{GetType(Bicycle), GetType(Tricycle)}
Protected Overrides Function CreateKnownType(ByVal index As Integer) As Object
Select Case index
Case 0
Return New Bicycle()
Case 1
Return New Tricycle()
Case Else
Throw New ArgumentOutOfRangeException("Unknown Type")
End Select
End Function
Protected Overrides Function GetKnownTypes() As Type()
Return _typesOfCycles
End Function
Protected Overrides Sub SetDirtyObject(ByVal o As Object)
CType(o, Cycle).SetDirty()
End Sub
End Class
'////////////////////////////////////////////////////////////
'
' The abstract Cycle class represents bicycles and tricycles.
'
'////////////////////////////////////////////////////////////
MustInherit Public Class Cycle
Implements IStateManager
Friend Protected Sub New(ByVal numWheels As Integer)
MyClass.New(numWheels, "Red")
End Sub
Friend Protected Sub New(ByVal numWheels As Integer, ByVal color As String)
numOfWheels = numWheels
CycleColor = color
End Sub
Private numOfWheels As Integer = 0
Public ReadOnly Property NumberOfWheels() As Integer
Get
Return numOfWheels
End Get
End Property
Public Property CycleColor() As String
Get
Dim o As Object = ViewState("Color")
If o Is Nothing Then
Return String.Empty
Else
Return o.ToString()
End If
End Get
Set
ViewState("Color") = value
End Set
End Property
Friend Sub SetDirty()
ViewState.SetDirty(True)
End Sub
' Because Cycle does not derive from Control, it does not
' have access to an inherited view state StateBag object.
Private cycleViewState As StateBag
Private ReadOnly Property ViewState() As StateBag
Get
If cycleViewState Is Nothing Then
cycleViewState = New StateBag(False)
If trackingViewState Then
CType(cycleViewState, IStateManager).TrackViewState()
End If
End If
Return cycleViewState
End Get
End Property
' The IStateManager implementation.
Private trackingViewState As Boolean
ReadOnly Property IsTrackingViewState() As Boolean _
Implements IStateManager.IsTrackingViewState
Get
Return trackingViewState
End Get
End Property
Sub LoadViewState(ByVal savedState As Object) _
Implements IStateManager.LoadViewState
Dim cycleState As Object() = CType(savedState, Object())
' In SaveViewState, an array of one element is created.
' Therefore, if the array passed to LoadViewState has
' more than one element, it is invalid.
If cycleState.Length <> 1 Then
Throw New ArgumentException("Invalid Cycle View State")
End If
' Call LoadViewState on the StateBag object.
CType(ViewState, IStateManager).LoadViewState(cycleState(0))
End Sub
' Save the view state by calling the StateBag's SaveViewState
' method.
Function SaveViewState() As Object Implements IStateManager.SaveViewState
Dim cycleState(0) As Object
If Not (cycleViewState Is Nothing) Then
cycleState(0) = _
CType(cycleViewState, IStateManager).SaveViewState()
End If
Return cycleState
End Function
' Begin tracking view state. Check the private variable, because
' if the view state has not been accessed or set, then it is not being
' used and there is no reason to store any view state.
Sub TrackViewState() Implements IStateManager.TrackViewState
trackingViewState = True
If Not (cycleViewState Is Nothing) Then
CType(cycleViewState, IStateManager).TrackViewState()
End If
End Sub
End Class
Public NotInheritable Class Bicycle
Inherits Cycle
' Create a red Cycle with two wheels.
Public Sub New()
MyBase.New(2)
End Sub
End Class
Public NotInheritable Class Tricycle
Inherits Cycle
' Create a red Cycle with three wheels.
Public Sub New()
MyBase.New(3)
End Sub
End Class
End Namespace
注解
该StateManagedCollection类是存储IStateManager元素（包括DataControlFieldCollection、、ParameterCollectionStyleCollection、TreeNodeBindingCollection和其他）的所有强类型集合的基类。 集合 StateManagedCollection 管理其自身的状态及其包含的元素的状态。 因此，调用保存 IStateManager.SaveViewState 集合的状态以及集合当前包含的所有元素的状态。
从StateManagedCollection类派生时要考虑的最重要方法包括CreateKnownType、GetKnownTypes、OnValidate和SetDirtySetDirtyObject。 GetKnownTypes和CreateKnownType方法用于将索引存储在包含元素类型的视图状态中。 存储索引而不是完全限定的类型名称可以提高性能。 OnValidate每当操作集合的元素时调用该方法，并根据业务规则验证元素。 目前，该方法的 OnValidate 实现禁止 null 对象存储在集合中;但是，可以重写此方法以在派生类型中定义自己的验证行为。 该方法 SetDirty 强制序列化整个集合以查看状态，而不仅仅是序列化自上次加载状态以来对状态所做的更改。 该方法 SetDirtyObject 是一种抽象方法，可用于在元素级别执行相同的行为。
重要
StateManagedCollection 将集合项的程序集限定类型名称存储在视图状态中。 网站访问者可以解码视图状态并检索类型名称。 如果此方案在网站中创建安全问题，则可以在将类型名称置于视图状态之前手动加密类型名称。
构造函数
| StateManagedCollection() |
初始化 StateManagedCollection 类的新实例。 |
属性
| Count |
获取 StateManagedCollection 集合中包含的元素的数量。 |
方法
显式接口实现
扩展方法
| Cast<TResult>(IEnumerable) |
将 IEnumerable 的元素强制转换为指定的类型。 |
| OfType<TResult>(IEnumerable) |
根据指定类型筛选 IEnumerable 的元素。 |
| AsParallel(IEnumerable) |
启用查询的并行化。 |
| AsQueryable(IEnumerable) |
将 IEnumerable 转换为 IQueryable。 |