如果你用Prism框架，那么请继续阅读本文，有关Scoped RegionManager的。Prism框架中有RegionManager，可以用构造注入IRegionManager的方式获得全局的RegionManager。今天要说的不是全局的RegionManager，而是Scoped RegionManager，也就是说在作用域内的RegionManager，什么意思？如果你的应用包含复杂的Region嵌套，例如，你的应用整体有一个大的TabRegion，每次打开一个Tab就是注入一个View，在每个View里面又各自包含TabRegion，里面每次打开一个Tab就是注入一个View，在每个View里面又各自包含TabRegion…..这样就是一个复合模式的Region嵌套了，这个时候，你如果关闭一个Tab又打开一个tab，或者打开多个同类型的tab，那就会遇到下列异常：
An exception occurred while trying to create region objects.
- The most likely causing exception was: 'System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. --->
Microsoft.Practices.Prism.Regions.Behaviors.RegionCreationException: An exception occurred while creating a region with name subTabSubRegion.
The exception was: System.ArgumentException: Region with the given name is already registered: subTabSubRegion
at Microsoft.Practices.Prism.Regions.RegionManager.RegionCollection.Add(IRegion region)
at Microsoft.Practices.Prism.Regions.Behaviors.RegionManagerRegistrationBehavior.TryRegisterRegion()
at Microsoft.Practices.Prism.Regions.Behaviors.RegionManagerRegistrationBehavior.StartMonitoringRegionManager()
at Microsoft.Practices.Prism.Regions.Behaviors.RegionManagerRegistrationBehavior.OnAttach()
at Microsoft.Practices.Prism.Regions.RegionBehavior.Attach()
at Microsoft.Practices.Prism.Regions.RegionBehaviorCollection.Add(String key, IRegionBehavior regionBehavior)
at Microsoft.Practices.Prism.Regions.RegionAdapterBase`1.AttachDefaultBehaviors(IRegion region, T regionTarget)
at Microsoft.Practices.Prism.Regions.RegionAdapterBase`1.Initialize(T regionTarget, String regionName)
at Microsoft.Practices.Prism.Regions.RegionAdapterBase`1.Microsoft.Practices.Prism.Regions.IRegionAdapter.Initialize(Object regionTarget, String regionName)
at Microsoft.Practices.Prism.Regions.Behaviors.DelayedRegionCreationBehavior.CreateRegion(DependencyObject targetElement, String regionName). ---> System.ArgumentException: Region with the given name is already registered: SubDevicesRegion
at Microsoft.Practices.Prism.Regions.RegionManager.RegionCollection.Add(IRegion region)
at Microsoft.Practices.Prism.Regions.Behaviors.RegionManagerRegistrationBehavior.TryRegisterRegion()
at Microsoft.Practices.Prism.Regions.Behaviors.RegionManagerRegistrationBehavior.StartMonitoringRegionManager()
at Microsoft.Practices.Prism.Regions.Behaviors.RegionManagerRegistrationBehavior.OnAttach()
at Microsoft.Practices.Prism.Regions.RegionBehavior.Attach()
at Microsoft.Practices.Prism.Regions.RegionBehaviorCollection.Add(String key, IRegionBehavior regionBehavior)
at Microsoft.Practices.Prism.Regions.RegionAdapterBase`1.AttachDefaultBehaviors(IRegion region, T regionTarget)
at Microsoft.Practices.Prism.Regions.RegionAdapterBase`1.Initialize(T regionTarget, String regionName)
at Microsoft.Practices.Prism.Regions.RegionAdapterBase`1.Microsoft.Practices.Prism.Regions.IRegionAdapter.Initialize(Object regionTarget, String regionName)
at Microsoft.Practices.Prism.Regions.Behaviors.DelayedRegionCreationBehavior.CreateRegion(DependencyObject targetElement, String regionName)
--- End of inner exception stack trace ---
at Microsoft.Practices.Prism.Regions.Behaviors.DelayedRegionCreationBehavior.CreateRegion(DependencyObject targetElement, String regionName)
at Microsoft.Practices.Prism.Regions.Behaviors.DelayedRegionCreationBehavior.TryCreateRegion()
at Microsoft.Practices.Prism.Regions.Behaviors.DelayedRegionCreationBehavior.OnUpdatingRegions(Object sender, EventArgs e)
--- End of inner exception stack trace ---
at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Delegate.DynamicInvoke(Object[] args)
at Microsoft.Practices.Prism.Events.WeakDelegatesManager.Raise(Object[] args)
at Microsoft.Practices.Prism.Regions.RegionManager.UpdateRegions()'.
解决这个问题的方法就是用Scoped Region，比如在打开的DetailsView的时候，用IRegionManaer r = region.add(view, key, true)方法，然后用创建的Scoped RegionManager新实例来打开新的视图，而不是用GLobal RegionManager。代码：
1: //注意返回值，注意最后一个参数
2: IRegionManager detailsRegionManager =
3: detailsRegion.Add(detailsPresenter.View,
4: employee.EmployeeId.ToString(CultureInfo.InvariantCulture), true);
5:
6: //用上面Scoped Regionmanager 新实例来加视图！
7: IRegion region = detailsRegionManager.Regions[RegionNames.TabRegion];
8: region.Add(projectsListPresenter.View, "CurrentProjectsView");
9: detailsRegion.Activate(detailsPresenter.View);
如果你用MVVM模式来开发，而且每次打开新的视图都是独立的MVVM的模式，那么问题就来了，这个Scoped RegionManager如何传递到新的视图的ViewModel？这就是ViewModel之间如何传递数据传参数的问题了。我使用扩展方法扩展了regionManager.RequestNavigate方法，添加ComplexData参数，这样我就可以把IRegionManager（Scoped RegionManager）放在ComplexData参数里面，用regionManager.RequestNavigate方法传递到新建View的ViewModel里面去，完全是两个ViewModel间传递参数。具体代码参考我的另外一篇博文，这里不重复了。
有关Scoped RegionManager其它资源：