Prism中Region（上）
目录
概述
在介绍Region之前我们首先有必要了解什么是Region(区域)简单来说，Region可以理解为View的动态占位符，在View上进行视图占位,就像在电影院占座一样，方便后续注入UI元素，比如我们可以将我们的程序划分为MenuRegion，Top Region、和Main Region，我们之前并不知道这几块区域到底会放置什么东西？因此我们先进行布局站位，比如使用ContentControl设置当前的区域名称，如下面的代码所示：
<ContentControl prism:RegionManager.RegionName="MenuRegion" />
在后面我们就可以根据需要为这个名称为MenuRegion的区域注入真正地View对象，这样做的目的是为了真正地实现界面的解耦，这个是整个Region设计的核心思想。
源码分析
1 IRegion接口
按照我们之前读源码系列的思路，我们首先还是从最基本的接口进行一个个分析。
/// <summary>
/// Defines a model that can be used to compose views.
/// </summary>
public interface IRegion : INavigateAsync, INotifyPropertyChanged
{
/// <summary>
/// Gets a readonly view of the collection of views in the region.
/// </summary>
/// <value>An <see cref="IViewsCollection"/> of all the added views.</value>
IViewsCollection Views { get; }
/// <summary>
/// Gets a readonly view of the collection of all the active views in the region.
/// </summary>
/// <value>An <see cref="IViewsCollection"/> of all the active views.</value>
IViewsCollection ActiveViews { get; }
/// <summary>
/// Gets or sets a context for the region. This value can be used by the user to share context with the views.
/// </summary>
/// <value>The context value to be shared.</value>
object Context { get; set; }
/// <summary>
/// Gets the name of the region that uniquely identifies the region within a <see cref="IRegionManager"/>.
/// </summary>
/// <value>The name of the region.</value>
string Name { get; set; }
/// <summary>
/// Gets or sets the comparison used to sort the views.
/// </summary>
/// <value>The comparison to use.</value>
Comparison<object> SortComparison { get; set; }
///<overloads>Adds a new view to the region.</overloads>
/// <summary>
/// Adds a new view to the region.
/// </summary>
/// <param name="view">The view to add.</param>
/// <returns>The <see cref="IRegionManager"/> that is set on the view if it is a <see cref="DependencyObject"/>. It will be the current region manager when using this overload.</returns>
IRegionManager Add(object view);
/// <summary>
/// Adds a new view to the region.
/// </summary>
/// <param name="view">The view to add.</param>
/// <param name="viewName">The name of the view. This can be used to retrieve it later by calling <see cref="GetView"/>.</param>
/// <returns>The <see cref="IRegionManager"/> that is set on the view if it is a <see cref="DependencyObject"/>. It will be the current region manager when using this overload.</returns>
IRegionManager Add(object view, string viewName);
/// <summary>
/// Adds a new view to the region.
/// </summary>
/// <param name="view">The view to add.</param>
/// <param name="viewName">The name of the view. This can be used to retrieve it later by calling <see cref="GetView"/>.</param>
/// <param name="createRegionManagerScope">When <see langword="true"/>, the added view will receive a new instance of <see cref="IRegionManager"/>, otherwise it will use the current region manager for this region.</param>
/// <returns>The <see cref="IRegionManager"/> that is set on the view if it is a <see cref="DependencyObject"/>.</returns>
IRegionManager Add(object view, string viewName, bool createRegionManagerScope);
/// <summary>
/// Removes the specified view from the region.
/// </summary>
/// <param name="view">The view to remove.</param>
void Remove(object view);
/// <summary>
/// Removes all views from the region.
/// </summary>
void RemoveAll();
/// <summary>
/// Marks the specified view as active.
/// </summary>
/// <param name="view">The view to activate.</param>
void Activate(object view);
/// <summary>
/// Marks the specified view as inactive.
/// </summary>
/// <param name="view">The view to deactivate.</param>
void Deactivate(object view);
/// <summary>
/// Returns the view instance that was added to the region using a specific name.
/// </summary>
/// <param name="viewName">The name used when adding the view to the region.</param>
/// <returns>Returns the named view or <see langword="null"/> if the view with <paramref name="viewName"/> does not exist in the current region.</returns>
object GetView(string viewName);
/// <summary>
/// Gets or sets the <see cref="IRegionManager"/> that will be passed to the views when adding them to the region, unless the view is added by specifying createRegionManagerScope as <see langword="true" />.
/// </summary>
/// <value>The <see cref="IRegionManager"/> where this <see cref="IRegion"/> is registered.</value>
/// <remarks>This is usually used by implementations of <see cref="IRegionManager"/> and should not be
/// used by the developer explicitly.</remarks>
IRegionManager RegionManager { get; set; }
/// <summary>
/// Gets the collection of <see cref="IRegionBehavior"/>s that can extend the behavior of regions.
/// </summary>
IRegionBehaviorCollection Behaviors { get; }
/// <summary>
/// Gets or sets the navigation service.
/// </summary>
/// <value>The navigation service.</value>
IRegionNavigationService NavigationService { get; set; }
}
在我们了解IRegion内部关联的对象之前，我们来看看IRegion接口继承了哪些接口，首先就是INavigateAsync接口，初一看这个接口不太清楚什么意思，但是我们可以通过类比浏览器的导航功能做一个对比，然后我们结合IRegion接口中定义的Views和ActiveViews属性我们便有一个清晰的认识就是一个IRegion中会有多个View我们可以通过传入不同的URL从而控制当前的Region中到底显示的是哪一个界面？这个场景是不是非常常见，想想一下我们的微信、QQ等软件，左侧是联系人，右边是具体信息界面，当我们点击左侧不同联系人时右侧的Region区域会显示不同的详细信息，而这些不同信息都是在一个Region中进行展示的，有了这个解释是不是非常形象。
1.1 INavigateAsync接口
/// <summary>
/// Provides methods to perform navigation.
/// </summary>
/// <remarks>
/// Convenience overloads for the methods in this interface can be found as extension methods on the
/// <see cref="NavigationAsyncExtensions"/> class.
/// </remarks>
public interface INavigateAsync
{
/// <summary>
/// Initiates navigation to the target specified by the <see cref="Uri"/>.
/// </summary>
/// <param name="target">The navigation target</param>
/// <param name="navigationCallback">The callback executed when the navigation request is completed.</param>
/// <remarks>
/// Convenience overloads for this method can be found as extension methods on the
/// <see cref="NavigationAsyncExtensions"/> class.
/// </remarks>
void RequestNavigate(Uri target, Action<NavigationResult> navigationCallback);
/// <summary>
/// Initiates navigation to the target specified by the <see cref="Uri"/>.
/// </summary>
/// <param name="target">The navigation target</param>
/// <param name="navigationCallback">The callback executed when the navigation request is completed.</param>
/// <param name="navigationParameters">The navigation parameters specific to the navigation request.</param>
/// <remarks>
/// Convenience overloads for this method can be found as extension methods on the
/// <see cref="NavigationAsyncExtensions"/> class.
/// </remarks>
void RequestNavigate(Uri target, Action<NavigationResult> navigationCallback, NavigationParameters navigationParameters);
}
IRegion实现的第二个接口是INotifyPropertyChanged接口，这个就不用做过多的解释主要就是属性变更通知UI的，这个就在这里不做过多解释。
在了解完了IRegion继承的外部接口之前我们先来了解其内如关联的相关接口
1.2 IViewsCollection接口
/// <summary>
/// Defines a view of a collection.
/// </summary>
public interface IViewsCollection : IEnumerable<object>, INotifyCollectionChanged
{
/// <summary>
/// Determines whether the collection contains a specific value.
/// </summary>
/// <param name="value">The object to locate in the collection.</param>
/// <returns><see langword="true" /> if <paramref name="value"/> is found in the collection; otherwise, <see langword="false" />.</returns>
bool Contains(object value);
}
这个是用在IRegion接口中的Views和ActiveViews属性的，我们刚才说过一个IRegion中包含多个View对象并且通过实现INavigateAsync接口来实现不同的视图对象的切换，这里通过接口定义我们大概就了解其内部的实现，围绕着这个 IViewsCollection对象我们发现在IRegion接口中关于View的Add、Remove、Active、DeActive都是和这个直接相关的，通过接口定义我们就能够对整个Region包含的功能有一个清晰的认知。
1.3 IRegionManager接口
这个我们将会在后面的文章中就这个做单独的分析，这里我们需要注意的是一个IRegion对应一个IRegionManager，一个IRegionManager用来管理当前IRegion中的各种View对象，本节我们不重点去介绍这个部分。
1.4 IRegionBehavior接口
这个我们也将会在后面的文章中就这个做单独的分析，这个接口主要是为当前的IRegion添加各种各种的Behavior，通过实现这个接口我们能为当前Region添加各种各样的行为而且代码结构上会更加统一和标准，这个也是Prism框架设计的优秀地方。
/// <summary>
/// Interface for allowing extensible behavior on regions.
/// </summary>
public interface IRegionBehavior
{
/// <summary>
/// The region that this behavior is extending.
/// </summary>
IRegion Region { get; set; }
/// <summary>
/// Attaches the behavior to the specified region.
/// </summary>
void Attach();
}
1.5 IRegionNavigationServicer接口
在上面的分析中我们发现IRegionNavigationService这个接口主要是实现IRegion中Views实现导航功能，这个IRegionNavigationService这个接口也实现了INavigateAsync这个接口，所以我们可以猜测IRegion中的导航功能最终是通过IRegion内部关联的
IRegionNavigationService接口实现的，而且IRegionNavigationService这个接口内部包含导航时的各种技术细节，并且通过时间向外通知当前导航的状态，这个部分后面我们也将分章节去介绍这个部分的具体实现。
/// <summary>
/// Provides navigation for regions.
/// </summary>
public interface IRegionNavigationService : INavigateAsync
{
/// <summary>
/// Gets or sets the region owning this service.
/// </summary>
/// <value>A Region.</value>
IRegion Region { get; set; }
/// <summary>
/// Gets the journal.
/// </summary>
/// <value>The journal.</value>
IRegionNavigationJournal Journal { get; }
/// <summary>
/// Raised when the region is about to be navigated to content.
/// </summary>
event EventHandler<RegionNavigationEventArgs> Navigating;
/// <summary>
/// Raised when the region is navigated to content.
/// </summary>
event EventHandler<RegionNavigationEventArgs> Navigated;
/// <summary>
/// Raised when a navigation request fails.
/// </summary>
event EventHandler<RegionNavigationFailedEventArgs> NavigationFailed;
}
至此通过对IRegion接口中的分析，我们对于整个Region的功能有一个大概的了解，并对每一个关联以及继承的接口都有清晰的认知，我们先抓住整个脉络从而对整体有一个清晰的认识，后面再深入细节，这样我们理解整个框架就容易多了。
2 Region实现
这个部分看着代码很多，其实有了上面的分析你大概对这个部分的具体实现是怎么样的？而且我们最重要的是学习这些框架的封装思想，这个才是最重要的。
/// <summary>
/// Implementation of <see cref="IRegion"/> that allows multiple active views.
/// </summary>
public class Region : IRegion
{
private ObservableCollection<ItemMetadata> _itemMetadataCollection;
private string _name;
private ViewsCollection _views;
private ViewsCollection _activeViews;
private object _context;
private IRegionManager _regionManager;
private IRegionNavigationService _regionNavigationService;
private Comparison<object> _sort;
/// <summary>
/// Initializes a new instance of <see cref="Region"/>.
/// </summary>
public Region()
{
Behaviors = new RegionBehaviorCollection(this);
_sort = DefaultSortComparison;
}
/// <summary>
/// Occurs when a property value changes.
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Gets the collection of <see cref="IRegionBehavior"/>s that can extend the behavior of regions.
/// </summary>
public IRegionBehaviorCollection Behaviors { get; }
/// <summary>
/// Gets or sets a context for the region. This value can be used by the user to share context with the views.
/// </summary>
/// <value>The context value to be shared.</value>
public object Context
{
get => _context;
set
{
if (_context != value)
{
_context = value;
OnPropertyChanged(nameof(Context));
}
}
}
/// <summary>
/// Gets the name of the region that uniquely identifies the region within a <see cref="IRegionManager"/>.
/// </summary>
/// <value>The name of the region.</value>
public string Name
{
get => _name;
set
{
if (_name != null && _name != value)
{
throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, Resources.CannotChangeRegionNameException, _name));
}
if (string.IsNullOrEmpty(value))
{
throw new ArgumentException(Resources.RegionNameCannotBeEmptyException);
}
_name = value;
OnPropertyChanged(nameof(Name));
}
}
/// <summary>
/// Gets a readonly view of the collection of views in the region.
/// </summary>
/// <value>An <see cref="IViewsCollection"/> of all the added views.</value>
public virtual IViewsCollection Views
{
get
{
if (_views == null)
{
_views = new ViewsCollection(ItemMetadataCollection, x => true)
{
SortComparison = _sort
};
}
return _views;
}
}
/// <summary>
/// Gets a readonly view of the collection of all the active views in the region.
/// </summary>
/// <value>An <see cref="IViewsCollection"/> of all the active views.</value>
public virtual IViewsCollection ActiveViews
{
get
{
if (_views == null)
{
_views = new ViewsCollection(ItemMetadataCollection, x => true)
{
SortComparison = _sort
};
}
if (_activeViews == null)
{
_activeViews = new ViewsCollection(ItemMetadataCollection, x => x.IsActive)
{
SortComparison = _sort
};
}
return _activeViews;
}
}
/// <summary>
/// Gets or sets the comparison used to sort the views.
/// </summary>
/// <value>The comparison to use.</value>
public Comparison<object> SortComparison
{
get => _sort;
set
{
_sort = value;
if (_activeViews != null)
{
_activeViews.SortComparison = _sort;
}
if (_views != null)
{
_views.SortComparison = _sort;
}
}
}
/// <summary>
/// Gets or sets the <see cref="IRegionManager"/> that will be passed to the views when adding them to the region, unless the view is added by specifying createRegionManagerScope as <see langword="true" />.
/// </summary>
/// <value>The <see cref="IRegionManager"/> where this <see cref="IRegion"/> is registered.</value>
/// <remarks>This is usually used by implementations of <see cref="IRegionManager"/> and should not be
/// used by the developer explicitly.</remarks>
public IRegionManager RegionManager
{
get => _regionManager;
set
{
if (_regionManager != value)
{
_regionManager = value;
OnPropertyChanged(nameof(RegionManager));
}
}
}
/// <summary>
/// Gets the navigation service.
/// </summary>
/// <value>The navigation service.</value>
public IRegionNavigationService NavigationService
{
get
{
if (_regionNavigationService == null)
{
_regionNavigationService = ContainerLocator.Container.Resolve<IRegionNavigationService>();
_regionNavigationService.Region = this;
}
return _regionNavigationService;
}
set => _regionNavigationService = value;
}
/// <summary>
/// Gets the collection with all the views along with their metadata.
/// </summary>
/// <value>An <see cref="ObservableCollection{T}"/> of <see cref="ItemMetadata"/> with all the added views.</value>
protected virtual ObservableCollection<ItemMetadata> ItemMetadataCollection
{
get
{
if (_itemMetadataCollection == null)
{
_itemMetadataCollection = new ObservableCollection<ItemMetadata>();
}
return _itemMetadataCollection;
}
}
/// <overloads>Adds a new view to the region.</overloads>
/// <summary>
/// Adds a new view to the region.
/// </summary>
/// <param name="view">The view to add.</param>
/// <returns>The <see cref="IRegionManager"/> that is set on the view if it is a <see cref="DependencyObject"/>. It will be the current region manager when using this overload.</returns>
public IRegionManager Add(object view)
{
return this.Add(view, null, false);
}
/// <summary>
/// Adds a new view to the region.
/// </summary>
/// <param name="view">The view to add.</param>
/// <param name="viewName">The name of the view. This can be used to retrieve it later by calling <see cref="IRegion.GetView"/>.</param>
/// <returns>The <see cref="IRegionManager"/> that is set on the view if it is a <see cref="DependencyObject"/>. It will be the current region manager when using this overload.</returns>
public IRegionManager Add(object view, string viewName)
{
if (string.IsNullOrEmpty(viewName))
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.StringCannotBeNullOrEmpty, "viewName"));
}
return this.Add(view, viewName, false);
}
/// <summary>
/// Adds a new view to the region.
/// </summary>
/// <param name="view">The view to add.</param>
/// <param name="viewName">The name of the view. This can be used to retrieve it later by calling <see cref="IRegion.GetView"/>.</param>
/// <param name="createRegionManagerScope">When <see langword="true"/>, the added view will receive a new instance of <see cref="IRegionManager"/>, otherwise it will use the current region manager for this region.</param>
/// <returns>The <see cref="IRegionManager"/> that is set on the view if it is a <see cref="DependencyObject"/>.</returns>
public virtual IRegionManager Add(object view, string viewName, bool createRegionManagerScope)
{
IRegionManager manager = createRegionManagerScope ? this.RegionManager.CreateRegionManager() : this.RegionManager;
this.InnerAdd(view, viewName, manager);
return manager;
}
/// <summary>
/// Removes the specified view from the region.
/// </summary>
/// <param name="view">The view to remove.</param>
public virtual void Remove(object view)
{
ItemMetadata itemMetadata = this.GetItemMetadataOrThrow(view);
ItemMetadataCollection.Remove(itemMetadata);
if (view is DependencyObject dependencyObject && Regions.RegionManager.GetRegionManager(dependencyObject) == this.RegionManager)
{
dependencyObject.ClearValue(Regions.RegionManager.RegionManagerProperty);
}
}
/// <summary>
/// Removes all views from the region.
/// </summary>
public void RemoveAll()
{
foreach (var view in Views)
{
Remove(view);
}
}
/// <summary>
/// Marks the specified view as active.
/// </summary>
/// <param name="view">The view to activate.</param>
public virtual void Activate(object view)
{
ItemMetadata itemMetadata = this.GetItemMetadataOrThrow(view);
if (!itemMetadata.IsActive)
{
itemMetadata.IsActive = true;
}
}
/// <summary>
/// Marks the specified view as inactive.
/// </summary>
/// <param name="view">The view to deactivate.</param>
public virtual void Deactivate(object view)
{
ItemMetadata itemMetadata = this.GetItemMetadataOrThrow(view);
if (itemMetadata.IsActive)
{
itemMetadata.IsActive = false;
}
}
/// <summary>
/// Returns the view instance that was added to the region using a specific name.
/// </summary>
/// <param name="viewName">The name used when adding the view to the region.</param>
/// <returns>Returns the named view or <see langword="null"/> if the view with <paramref name="viewName"/> does not exist in the current region.</returns>
public virtual object GetView(string viewName)
{
if (string.IsNullOrEmpty(viewName))
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.StringCannotBeNullOrEmpty, "viewName"));
}
ItemMetadata metadata = this.ItemMetadataCollection.FirstOrDefault(x => x.Name == viewName);
if (metadata != null)
{
return metadata.Item;
}
return null;
}
/// <summary>
/// Initiates navigation to the specified target.
/// </summary>
/// <param name="target">The target.</param>
/// <param name="navigationCallback">A callback to execute when the navigation request is completed.</param>
public void RequestNavigate(Uri target, Action<NavigationResult> navigationCallback)
{
this.RequestNavigate(target, navigationCallback, null);
}
/// <summary>
/// Initiates navigation to the specified target.
/// </summary>
/// <param name="target">The target.</param>
/// <param name="navigationCallback">A callback to execute when the navigation request is completed.</param>
/// <param name="navigationParameters">The navigation parameters specific to the navigation request.</param>
public void RequestNavigate(Uri target, Action<NavigationResult> navigationCallback, NavigationParameters navigationParameters)
{
this.NavigationService.RequestNavigate(target, navigationCallback, navigationParameters);
}
private void InnerAdd(object view, string viewName, IRegionManager scopedRegionManager)
{
if (this.ItemMetadataCollection.FirstOrDefault(x => x.Item == view) != null)
{
throw new InvalidOperationException(Resources.RegionViewExistsException);
}
ItemMetadata itemMetadata = new ItemMetadata(view);
if (!string.IsNullOrEmpty(viewName))
{
if (this.ItemMetadataCollection.FirstOrDefault(x => x.Name == viewName) != null)
{
throw new InvalidOperationException(String.Format(CultureInfo.InvariantCulture, Resources.RegionViewNameExistsException, viewName));
}
itemMetadata.Name = viewName;
}
if (view is DependencyObject dependencyObject)
{
Regions.RegionManager.SetRegionManager(dependencyObject, scopedRegionManager);
}
this.ItemMetadataCollection.Add(itemMetadata);
}
private ItemMetadata GetItemMetadataOrThrow(object view)
{
if (view == null)
throw new ArgumentNullException(nameof(view));
ItemMetadata itemMetadata = this.ItemMetadataCollection.FirstOrDefault(x => x.Item == view);
if (itemMetadata == null)
throw new ArgumentException(Resources.ViewNotInRegionException, nameof(view));
return itemMetadata;
}
private void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
/// <summary>
/// The default sort algorithm.
/// </summary>
/// <param name="x">The first view to compare.</param>
/// <param name="y">The second view to compare.</param>
/// <returns></returns>
[SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "y")]
[SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "x")]
public static int DefaultSortComparison(object x, object y)
{
if (x == null)
{
if (y == null)
{
return 0;
}
else
{
return -1;
}
}
else
{
if (y == null)
{
return 1;
}
else
{
Type xType = x.GetType();
Type yType = y.GetType();
ViewSortHintAttribute xAttribute = xType.GetCustomAttributes(typeof(ViewSortHintAttribute), true).FirstOrDefault() as ViewSortHintAttribute;
ViewSortHintAttribute yAttribute = yType.GetCustomAttributes(typeof(ViewSortHintAttribute), true).FirstOrDefault() as ViewSortHintAttribute;
return ViewSortHintAttributeComparison(xAttribute, yAttribute);
}
}
}
private static int ViewSortHintAttributeComparison(ViewSortHintAttribute x, ViewSortHintAttribute y)
{
if (x == null)
{
if (y == null)
{
return 0;
}
else
{
return -1;
}
}
else
{
if (y == null)
{
return 1;
}
else
{
return string.Compare(x.Hint, y.Hint, StringComparison.Ordinal);
}
}
}
}
2.1 Region中Views的管理
这个部分我就不做每一部分代码详细分析了，重点缕清楚其背后设计的思想。首先无论是Views还是ActiveViews代码中通过一个ObservableCollection
2.2 Region中的Context
在当前的Region中暂时没看清楚这个Context的作用，不过其注释其实说的很清楚就是为这些Views提供一个共享的数据上下文。
/// <summary>
/// Gets or sets a context for the region. This value can be used by the user to share context with the views.
/// </summary>
/// <value>The context value to be shared.</value>
public object Context
{
get => _context;
set
{
if (_context != value)
{
_context = value;
OnPropertyChanged(nameof(Context));
}
}
}
2.3 Region中的Navigation
IRegion中实现了INavigateAsync接口实现了View的导航功能，在Region的内部是通过一个前面分析过的IRegionNavigationService类型的NavigationService去实现的，其内部的具体原理后面分析具体代码的时候再进行讲述。
2.4 Region中的SortComparison
我们在看Region这个部分的代码时我们发现，很多的篇幅是介绍同一个Region内部多个Views的排序规则的，这个主要是通过定义一个规则让这些Views有一个先后顺序，这个决定后面View加载的一些细节，甚至我们可以看到通过在View上面添加自定义属性ViewSortHint我们能够人为的对其先后顺序进行排序，这个需要注意。
public static int DefaultSortComparison(object x, object y)
{
if (x == null)
{
if (y == null)
{
return 0;
}
else
{
return -1;
}
}
else
{
if (y == null)
{
return 1;
}
else
{
Type xType = x.GetType();
Type yType = y.GetType();
ViewSortHintAttribute xAttribute = xType.GetCustomAttributes(typeof(ViewSortHintAttribute), true).FirstOrDefault() as ViewSortHintAttribute;
ViewSortHintAttribute yAttribute = yType.GetCustomAttributes(typeof(ViewSortHintAttribute), true).FirstOrDefault() as ViewSortHintAttribute;
return ViewSortHintAttributeComparison(xAttribute, yAttribute);
}
}
}
总结
有了上面从IRegion接口的定义到IRegion接口的实现我们对整个Prism框架中的Region有一个清晰的认知，在后面的章节中我们将会对其中的技术细节，比如IRegionManager、IRegionNavigationService的具体实现分章节进行一一讲述，力求将整个Prism框架中由外到内，由总体到局部一一分析从而使自己有一个更加清晰的认知。
