//===================================================================================
// Microsoft patterns & practices
// Composite Application Guidance for Windows Presentation Foundation and Silverlight
//===================================================================================
// Copyright (c) Microsoft Corporation. All rights reserved.
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT
// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS FOR A PARTICULAR PURPOSE.
//===================================================================================
// The example companies, organizations, products, domain names,
// e-mail addresses, logos, people, places, and events depicted
// herein are fictitious. No association with any real company,
// organization, product, domain name, email address, logo, person,
// places, or events is intended or should be inferred.
//===================================================================================
using System;
using System.Linq;
using System.Windows.Threading;
using Microsoft.Practices.Composite.Events;
namespace Microsoft.Practices.Composite.Presentation.Events
{
/// <summary>
/// Defines a class that manages publication and subscription to events.
/// </summary>
/// <typeparam name="TPayload">The type of message that will be passed to the subscribers.</typeparam>
public class CompositePresentationEvent<TPayload> : EventBase
{
private IDispatcherFacade uiDispatcher;
/// <summary>
/// Gets the <see cref="Dispatcher"/> that is bound to the UI elements.
/// </summary>
/// <value>The <see cref="Dispatcher"/> to use when subscribing using <see cref="ThreadOption.UIThread"/>.</value>
private IDispatcherFacade UIDispatcher
{
get
{
if (uiDispatcher == null)
{
this.uiDispatcher = new DefaultDispatcher();
}
return uiDispatcher;
}
}
/// <summary>
/// Subscribes a delegate to an event that will be published on the <see cref="ThreadOption.PublisherThread"/>.
/// <see cref="CompositePresentationEvent{TPayload}"/> will maintain a <seealso cref="WeakReference"/> to the target of the supplied <paramref name="action"/> delegate.
/// </summary>
/// <param name="action">The delegate that gets executed when the event is published.</param>
/// <returns>A <see cref="SubscriptionToken"/> that uniquely identifies the added subscription.</returns>
/// <remarks>
/// The CompositePresentationEvent collection is thread-safe.
/// </remarks>
public SubscriptionToken Subscribe(Action<TPayload> action)
{
return Subscribe(action, ThreadOption.PublisherThread);
}
/// <summary>
/// Subscribes a delegate to an event.
/// CompositePresentationEvent will maintain a <seealso cref="WeakReference"/> to the Target of the supplied <paramref name="action"/> delegate.
/// </summary>
/// <param name="action">The delegate that gets executed when the event is raised.</param>
/// <param name="threadOption">Specifies on which thread to receive the delegate callback.</param>
/// <returns>A <see cref="SubscriptionToken"/> that uniquely identifies the added subscription.</returns>
/// <remarks>
/// The CompositePresentationEvent collection is thread-safe.
/// </remarks>
public SubscriptionToken Subscribe(Action<TPayload> action, ThreadOption threadOption)
{
return Subscribe(action, threadOption, false);
}
/// <summary>
/// Subscribes a delegate to an event that will be published on the <see cref="ThreadOption.PublisherThread"/>.
/// </summary>
/// <param name="action">The delegate that gets executed when the event is published.</param>
/// <param name="keepSubscriberReferenceAlive">When <see langword="true"/>, the <seealso cref="CompositePresentationEvent{TPayload}"/> keeps a reference to the subscriber so it does not get garbage collected.</param>
/// <returns>A <see cref="SubscriptionToken"/> that uniquely identifies the added subscription.</returns>
/// <remarks>
/// If <paramref name="keepSubscriberReferenceAlive"/> is set to <see langword="false" />, <see cref="CompositePresentationEvent{TPayload}"/> will maintain a <seealso cref="WeakReference"/> to the Target of the supplied <paramref name="action"/> delegate.
/// If not using a WeakReference (<paramref name="keepSubscriberReferenceAlive"/> is <see langword="true" />), the user must explicitly call Unsubscribe for the event when disposing the subscriber in order to avoid memory leaks or unexepcted behavior.
///
/// The CompositePresentationEvent collection is thread-safe.
/// </remarks>
public SubscriptionToken Subscribe(Action<TPayload> action, bool keepSubscriberReferenceAlive)
{
return Subscribe(action, ThreadOption.PublisherThread, keepSubscriberReferenceAlive);
}
/// <summary>
/// Subscribes a delegate to an event.
/// </summary>
/// <param name="action">The delegate that gets executed when the event is published.</param>
/// <param name="threadOption">Specifies on which thread to receive the delegate callback.</param>
/// <param name="keepSubscriberReferenceAlive">When <see langword="true"/>, the <seealso cref="CompositePresentationEvent{TPayload}"/> keeps a reference to the subscriber so it does not get garbage collected.</param>
/// <returns>A <see cref="SubscriptionToken"/> that uniquely identifies the added subscription.</returns>
/// <remarks>
/// If <paramref name="keepSubscriberReferenceAlive"/> is set to <see langword="false" />, <see cref="CompositePresentationEvent{TPayload}"/> will maintain a <seealso cref="WeakReference"/> to the Target of the supplied <paramref name="action"/> delegate.
/// If not using a WeakReference (<paramref name="keepSubscriberReferenceAlive"/> is <see langword="true" />), the user must explicitly call Unsubscribe for the event when disposing the subscriber in order to avoid memory leaks or unexepcted behavior.
///
/// The CompositePresentationEvent collection is thread-safe.
/// </remarks>
public SubscriptionToken Subscribe(Action<TPayload> action, ThreadOption threadOption, bool keepSubscriberReferenceAlive)
{
return Subscribe(action, threadOption, keepSubscriberReferenceAlive, null);
}
/// <summary>
/// Subscribes a delegate to an event.
/// </summary>
/// <param name="action">The delegate that gets executed when the event is published.</param>
/// <param name="threadOption">Specifies on which thread to receive the delegate callback.</param>
/// <param name="keepSubscriberReferenceAlive">When <see langword="true"/>, the <seealso cref="CompositePresentationEvent{TPayload}"/> keeps a reference to the subscriber so it does not get garbage collected.</param>
/// <param name="filter">Filter to evaluate if the subscriber should receive the event.</param>
/// <returns>A <see cref="SubscriptionToken"/> that uniquely identifies the added subscription.</returns>
/// <remarks>
/// If <paramref name="keepSubscriberReferenceAlive"/> is set to <see langword="false" />, <see cref="CompositePresentationEvent{TPayload}"/> will maintain a <seealso cref="WeakReference"/> to the Target of the supplied <paramref name="action"/> delegate.
/// If not using a WeakReference (<paramref name="keepSubscriberReferenceAlive"/> is <see langword="true" />), the user must explicitly call Unsubscribe for the event when disposing the subscriber in order to avoid memory leaks or unexepcted behavior.
///
/// The CompositePresentationEvent collection is thread-safe.
/// </remarks>
public virtual SubscriptionToken Subscribe(Action<TPayload> action, ThreadOption threadOption, bool keepSubscriberReferenceAlive, Predicate<TPayload> filter)
{
IDelegateReference actionReference = new DelegateReference(action, keepSubscriberReferenceAlive);
IDelegateReference filterReference;
if (filter != null)
{
filterReference = new DelegateReference(filter, keepSubscriberReferenceAlive);
}
else
{
filterReference = new DelegateReference(new Predicate<TPayload>(delegate { return true; }), true);
}
EventSubscription<TPayload> subscription;
switch (threadOption)
{
case ThreadOption.PublisherThread:
subscription = new EventSubscription<TPayload>(actionReference, filterReference);
break;
case ThreadOption.BackgroundThread:
subscription = new BackgroundEventSubscription<TPayload>(actionReference, filterReference);
break;
case ThreadOption.UIThread:
subscription = new DispatcherEventSubscription<TPayload>(actionReference, filterReference, UIDispatcher);
break;
default:
subscription = new EventSubscription<TPayload>(actionReference, filterReference);
break;
}
return base.InternalSubscribe(subscription);
}
/// <summary>
/// Publishes the <see cref="CompositePresentationEvent{TPayload}"/>.
/// </summary>
/// <param name="payload">Message to pass to the subscribers.</param>
public virtual void Publish(TPayload payload)
{
base.InternalPublish(payload);
}
/// <summary>
/// Removes the first subscriber matching <seealso cref="Action{TPayload}"/> from the subscribers' list.
/// </summary>
/// <param name="subscriber">The <see cref="Action{TPayload}"/> used when subscribing to the event.</param>
public virtual void Unsubscribe(Action<TPayload> subscriber)
{
lock (Subscriptions)
{
IEventSubscription eventSubscription = Subscriptions.Cast<EventSubscription<TPayload>>().FirstOrDefault(evt => evt.Action == subscriber);
if (eventSubscription != null)
{
Subscriptions.Remove(eventSubscription);
}
}
}
/// <summary>
/// Returns <see langword="true"/> if there is a subscriber matching <seealso cref="Action{TPayload}"/>.
/// </summary>
/// <param name="subscriber">The <see cref="Action{TPayload}"/> used when subscribing to the event.</param>
/// <returns><see langword="true"/> if there is an <seealso cref="Action{TPayload}"/> that matches; otherwise <see langword="false"/>.</returns>
public virtual bool Contains(Action<TPayload> subscriber)
{
IEventSubscription eventSubscription;
lock (Subscriptions)
{
eventSubscription = Subscriptions.Cast<EventSubscription<TPayload>>().FirstOrDefault(evt => evt.Action == subscriber);
}
return eventSubscription != null;
}
}
}