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.

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.

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 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
Available since 2.0
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