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StateManagedCollection.CreateKnownType Method

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.

Namespace:  System.Web.UI
Assembly:  System.Web (in System.Web.dll)

protected virtual Object CreateKnownType(
	int index
)

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.Object
An instance of a class derived from IStateManager, according to the index provided.

ExceptionCondition
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 IStateManagerLoadViewState(Object) 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 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();
    }

}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

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.

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