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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
//
// Description:
// PageFunctions are the "atom" of Structured Navigation,
// this is the base element class from which the developer derives
// from to enable returning results to a caller.
//
using System.Windows.Controls;
using MS.Internal.AppModel;
namespace System.Windows.Navigation
{
///<summary>
/// Abstract base class for the generic PageFunction class.
///</summary>
public abstract class PageFunctionBase : Page
{
#region Constructors
///<summary>
/// PageFunctionBase constructor
///</summary>
protected PageFunctionBase()
{
// Make a new GUID for this ID, set the parent ID to 0-0-0-0-0
PageFunctionId = Guid.NewGuid();
ParentPageFunctionId = Guid.Empty;
}
#endregion Constructors
#region Public Properties
///<summary>
/// When set to true, the pagefunction with this property set and all child page functions will get removed from the journal.
/// This allows easy building of "transactioned" UI. If a series of steps have been completed, and it doesn't make sense to hit the back button and submit that transaction again,
/// setting this property enables those series of steps to be removed from the journal.
///</summary>
///<remarks>
/// Examples abound of "transactioned UI" buying a book from an ecommerce application, selling stock, creating a user account.
///</remarks>
public bool RemoveFromJournal
{
get
{
return _fRemoveFromJournal;
}
set
{
_fRemoveFromJournal = value;
}
}
#endregion Public Properties
#region Protected Methods
///<summary>
/// This method is called when a PageFunction is first navigated to.
/// It is not called when a Pagefunction resumes.
///</summary>
///<remarks>
/// Typically a developer will write some initialization code in their Start method,
/// or they may decide to invoke a child PageFunction.
///</remarks>
protected virtual void Start()
{
}
/*
/// <summary>
/// To be used by derived classes to raise strongly types return events. Must be overriden.
/// </summary>
// protected abstract void RaiseTypedReturnEvent(Delegate d, object returnEventArgs);
*/
#endregion Protected Methods
#region Internal Methods
// An internal method which is used to invoke the protected Start() method by
// other parts of the PageFunction code base.
internal void CallStart()
{
Start();
}
///<summary>
/// A Pagefunction calls this method to signal that it is completed and the ReturnEventArgs
/// will be supplied to the listener on Return ( and that listener will be unsuspended).
///</summary>
internal void _OnReturnUnTyped(object o)
{
if (_finish != null)
{
_finish(this, o);
}
}
internal void _AddEventHandler(Delegate d)
{
// This is where the parent-child relationship is established. If
// PageFunction A attaches one of its methods to PageFunction B's
// Return event, then A must be B's parent.
PageFunctionBase parent = d.Target as PageFunctionBase;
if (parent != null)
{
ParentPageFunctionId = parent.PageFunctionId;
}
_returnHandler = Delegate.Combine(_returnHandler, d);
}
internal void _RemoveEventHandler(Delegate d)
{
_returnHandler = Delegate.Remove(_returnHandler, d);
}
internal void _DetachEvents()
{
_returnHandler = null;
}
//
// Raise the event on the _returnHandler
//
internal void _OnFinish(object returnEventArgs)
{
RaiseTypedEventArgs args = new RaiseTypedEventArgs(_returnHandler, returnEventArgs);
RaiseTypedEvent(this, args);
//RaiseTypedReturnEvent(_returnHandler, returnEventArgs);
}
#endregion Internal Methods
#region Internal Properties
/// <summary>
/// This is the GUID for this PageFunction. It will be used as its childrens'
/// ParentPageFunctionId.
/// </summary>
internal Guid PageFunctionId
{
get { return _pageFunctionId; }
set { _pageFunctionId = value; }
}
/// <summary>
/// If this PageFunction is a child PageFunction, this will be the GUID of its
/// parent PageFunction. If this is Guid.Empty, then the parent is NOT a
/// PageFunction.
/// </summary>
internal Guid ParentPageFunctionId
{
get { return _parentPageFunctionId; }
set { _parentPageFunctionId = value; }
}
internal Delegate _Return
{
get { return _returnHandler; }
}
/// <summary>
/// Whether the PF is being resumed after a child PF returns OR due to journal navigation
/// (Go Back/Fwd)
/// </summary>
internal bool _Resume
{
get { return _resume; }
set { _resume = value; }
}
internal ReturnEventSaver _Saver
{
get { return _saverInfo; }
set { _saverInfo = value; }
}
#endregion Internal Properties
#region Internal Events
//
// The FinishEventHandler is used to communicate between the NavigationService and the ending Pagefunction
//
internal FinishEventHandler FinishHandler
{
get { return _finish; }
set { _finish = value; }
}
internal event EventToRaiseTypedEvent RaiseTypedEvent;
#endregion
#region Private Fields
private Guid _pageFunctionId;
private Guid _parentPageFunctionId;
private bool _fRemoveFromJournal = true; // new default, to make PFs behave more like functions
private bool _resume;
private ReturnEventSaver _saverInfo; // keeps track of Parent caller's Return Event Info
private FinishEventHandler _finish;
private Delegate _returnHandler; // the delegate for the Return event
#endregion Private Fields
}
internal delegate void EventToRaiseTypedEvent(PageFunctionBase sender, RaiseTypedEventArgs args);
internal class RaiseTypedEventArgs : System.EventArgs
{
internal RaiseTypedEventArgs(Delegate d, object o)
{
D = d;
O = o;
}
internal Delegate D;
internal Object O;
}
///<summary>
/// A callback handler used to receive a ReturnEventArgs of type T
///</summary>
public delegate void ReturnEventHandler<T>(object sender, ReturnEventArgs<T> e);
///<summary>
/// PageFunctions are the "atom" of Structured Navigation,
/// this is the base element class from which the developer derives
/// from to enable returning results to a caller.
///</summary>
/// <remarks>
/// Right now Pagefunctions are non-cls compliant owing to their use of generics. It is expected in the LH timeframe that
/// all CLS languages will support generics.
/// </remarks>
public class PageFunction<T> : PageFunctionBase
{
#region Constructors
///<summary>
/// Pagefunction constructor
///</summary>
public PageFunction()
{
RaiseTypedEvent += new EventToRaiseTypedEvent(RaiseTypedReturnEvent);
}
#endregion Constructors
#region Protected Methods
///<summary>
/// A Pagefunction calls this method to signal that it is completed and the ReturnEventArgs
/// will be supplied to the listener on Return ( and that listener will be unsuspended).
///</summary>
protected virtual void OnReturn(ReturnEventArgs<T> e)
{
_OnReturnUnTyped(e);
}
///<summary>
/// Used to raise a strongly typed return event. Sealed since nobody should have the need to override as
/// all derived types of this generic type will automatically get the strongly typed version from this
/// generic version.
///</summary>
internal void RaiseTypedReturnEvent(PageFunctionBase b, RaiseTypedEventArgs args)
{
Delegate d = args.D;
object returnEventArgs = args.O;
if (d != null)
{
ReturnEventArgs<T> ra = returnEventArgs as ReturnEventArgs<T>;
Debug.Assert((returnEventArgs == null) || (ra != null));
ReturnEventHandler<T> eh = d as ReturnEventHandler<T>;
Debug.Assert(eh != null);
eh(this, ra);
}
}
#endregion Protected Methods
#region Public Events
///<summary>
/// This is the event to which a caller will listen to get results returned.
///</summary>
public event ReturnEventHandler<T> Return
{
// We need to provide a way to surface out
// the listeners to the event
// So we override add/remove and keep track of it here.
add
{
_AddEventHandler((Delegate)value);
}
remove
{
_RemoveEventHandler((Delegate)value);
}
}
#endregion Public Events
}
}
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