StateManagedCollection.CreateKnownType Method (Int32)
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.
Assembly: System.Web (in System.Web.dll)
Parameters
- index
-
Type:
System.Int32
The index, from the ordered list of types returned by GetKnownTypes, of the type of IStateManager to create.
Return Value
Type: System.ObjectAn instance of a class derived from IStateManager, according to the index provided.
| Exception | Condition |
|---|---|
| InvalidOperationException | In all cases when not overridden in a derived class. |
The CreateKnownType method is called internally by the StateManagedCollection collection in its implementation of the StateManagedCollection.IStateManager.LoadViewState method. Derived collections override the CreateKnownType method to return a default instance of the IStateManager type identified by the provided index, which maps to one of the types returned by the GetKnownTypes method.
The following code example demonstrates how a strongly typed StateManagedCollection class implements the CreateKnownType method. The CycleCollection implementation of CreateKnownType returns the default instance of either a Bicycle or Tricycle object, depending on the index passed. This code example is part of a larger example provided for the StateManagedCollection class.
'//////////////////////////////////////////////////////////// ' ' 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
Available since 2.0