StateManagedCollection.GetKnownTypes Method

Definition

When overridden in a derived class, gets an array of IStateManager types that the StateManagedCollection collection can contain.

protected:
 virtual cli::array <Type ^> ^ GetKnownTypes();
protected virtual Type[] GetKnownTypes ();
abstract member GetKnownTypes : unit -> Type[]
override this.GetKnownTypes : unit -> Type[]
Protected Overridable Function GetKnownTypes () As Type()

Returns

Type[]

An ordered array of Type objects that identify the types of IStateManager objects the collection can contain. The default implementation returns null.

Examples

The following code example demonstrates how a strongly typed StateManagedCollection class implements the GetKnownTypes method. The CycleCollection implementation of GetKnownTypes returns a Type array of known types, including Bicycle and Tricycle types. 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 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 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

Remarks

The GetKnownTypes method is called internally by the StateManagedCollection collection in its implementation of the IStateManager.SaveViewState method. Derived collections override the GetKnownTypes method to return an array of Type objects that represent the types the collection can contain.

Applies to

See also