StateManagedCollection Class
Provides a base class for all strongly typed collections that manage IStateManager objects.
Assembly: System.Web (in System.Web.dll)
The StateManagedCollection type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | StateManagedCollection | Initializes a new instance of the StateManagedCollection class. |
| Name | Description | |
|---|---|---|
![]() | Clear | Removes all items from the StateManagedCollection collection. |
![]() | CopyTo | Copies the elements of the StateManagedCollection collection to an array, starting at a particular array index. |
![]() | CreateKnownType | When overridden in a derived class, creates an instance of a class that implements IStateManager. The type of object created is based on the specified member of the collection returned by the GetKnownTypes method. |
![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() | GetEnumerator | Returns an iterator that iterates through the StateManagedCollection collection. |
![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() | GetKnownTypes | When overridden in a derived class, gets an array of IStateManager types that the StateManagedCollection collection can contain. |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | OnClear | When overridden in a derived class, performs additional work before the Clear method removes all items from the collection. |
![]() | OnClearComplete | When overridden in a derived class, performs additional work after the Clear method finishes removing all items from the collection. |
![]() | OnInsert | When overridden in a derived class, performs additional work before the Insert(Int32, Object) or Add(Object) method adds an item to the collection. |
![]() | OnInsertComplete | When overridden in a derived class, performs additional work after the Insert(Int32, Object) or Add(Object) method adds an item to the collection. |
![]() | OnRemove | When overridden in a derived class, performs additional work before the Remove(Object) or RemoveAt(Int32) method removes the specified item from the collection. |
![]() | OnRemoveComplete | When overridden in a derived class, performs additional work after the Remove(Object) or RemoveAt(Int32) method removes the specified item from the collection. |
![]() | OnValidate | When overridden in a derived class, validates an element of the StateManagedCollection collection. |
![]() | SetDirty | Forces the entire StateManagedCollection collection to be serialized into view state. |
![]() | SetDirtyObject | When overridden in a derived class, instructs an object contained by the collection to record its entire state to view state, rather than recording only change information. |
![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
| Name | Description | |
|---|---|---|
![]() | AsParallel | Enables parallelization of a query. (Defined by ParallelEnumerable.) |
![]() | AsQueryable | Converts an IEnumerable to an IQueryable. (Defined by Queryable.) |
![]() | Cast(Of TResult) | Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.) |
![]() | OfType(Of TResult) | Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.) |
| Name | Description | |
|---|---|---|
![]() ![]() | ICollection.Count | Infrastructure. Gets the number of elements contained in the StateManagedCollection collection. |
![]() ![]() | ICollection.IsSynchronized | Infrastructure. Gets a value indicating whether the StateManagedCollection collection is synchronized (thread safe). This method returns false in all cases. |
![]() ![]() | ICollection.SyncRoot | Infrastructure. Gets an object that can be used to synchronize access to the StateManagedCollection collection. This method returns Nothing in all cases. |
![]() ![]() | IEnumerable.GetEnumerator | Infrastructure. Returns an iterator that iterates through the StateManagedCollection collection. |
![]() ![]() | IList.Add | Adds an item to the StateManagedCollection collection. |
![]() ![]() | IList.Clear | Infrastructure. Removes all items from the StateManagedCollection collection. |
![]() ![]() | IList.Contains | Determines whether the StateManagedCollection collection contains a specific value. |
![]() ![]() | IList.IndexOf | Determines the index of a specified item in the StateManagedCollection collection. |
![]() ![]() | IList.Insert | Inserts an item into the StateManagedCollection collection at the specified index. |
![]() ![]() | IList.IsFixedSize | Infrastructure. Gets a value indicating whether the StateManagedCollection collection has a fixed size. This method returns false in all cases. |
![]() ![]() | IList.IsReadOnly | Infrastructure. Gets a value indicating whether the StateManagedCollection collection is read-only. |
![]() ![]() | IList.Item | Infrastructure. Gets the IStateManager element at the specified index. |
![]() ![]() | IList.Remove | Removes the first occurrence of the specified object from the StateManagedCollection collection. |
![]() ![]() | IList.RemoveAt | Removes the IStateManager element at the specified index. |
![]() ![]() | IStateManager.IsTrackingViewState | Gets a value indicating whether the StateManagedCollection collection is saving changes to its view state. |
![]() ![]() | IStateManager.LoadViewState | Restores the previously saved view state of the StateManagedCollection collection and the IStateManager items it contains. |
![]() ![]() | IStateManager.SaveViewState | Saves the changes to the StateManagedCollection collection and each IStateManager object it contains since the time the page was posted back to the server. |
![]() ![]() | IStateManager.TrackViewState | Causes the StateManagedCollection collection and each of the IStateManager objects it contains to track changes to their view state so they can be persisted across requests for the same page. |
The StateManagedCollection class is the base class for all strongly typed collections that store IStateManager elements, including DataControlFieldCollection, ParameterCollection, StyleCollection, TreeNodeBindingCollection, and others. The StateManagedCollection collection manages its own state as well as the state of the elements it contains. Therefore, a call to SaveViewState saves the state of the collection and the state of all the elements currently contained by the collection.
The most important methods to consider when deriving from the StateManagedCollection class are CreateKnownType, GetKnownTypes, OnValidate, SetDirty, and SetDirtyObject. The CreateKnownType and GetKnownTypes methods are used to store an index in view state for the type of a contained element. Storing an index rather than a fully qualified type name improves performance. The OnValidate method is called whenever elements of the collection are manipulated, and validates the elements according to business rules. Currently, the implementation of the OnValidate method prohibits Nothing objects from being stored in the collection; however, you can override this method to define your own validation behavior in a derived type. The SetDirty method forces the entire collection to be serialized to view state, rather than just serializing changes made to state since the last time it was loaded. The SetDirtyObject method is an abstract method you can implement to perform this same behavior at the element level.
Security Note |
|---|
StateManagedCollection stores assembly-qualified type names of the collection items in view state. A site visitor could decode the view state and retrieve the type name. If this scenario creates a security concern in your Web site, you can manually encrypt the type name before placing it in the view state. |
The following code example demonstrates how to derive a strongly typed collection class from StateManagedCollection to contain IStateManager objects. In this example, the CycleCollection is derived to contain instances of the abstract Cycle class, which can be either Bicycle or Tricycle objects. The Cycle class implements the IStateManager interface because it stores the value of the CycleColor property in view state.
Imports System 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
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
System.Web.UI.StateManagedCollection
System.Web.UI.WebControls.DataControlFieldCollection
System.Web.UI.WebControls.DataPagerFieldCollection
System.Web.UI.WebControls.Expressions.DataSourceExpressionCollection
System.Web.UI.WebControls.HotSpotCollection
System.Web.UI.WebControls.MenuItemBindingCollection
System.Web.UI.WebControls.MenuItemStyleCollection
System.Web.UI.WebControls.ParameterCollection
System.Web.UI.WebControls.StyleCollection
System.Web.UI.WebControls.SubMenuStyleCollection
System.Web.UI.WebControls.TreeNodeBindingCollection
System.Web.UI.WebControls.TreeNodeStyleCollection

