我使用WPF Prism创建了一个小型演示应用程序,我正在使用Mef。
以下是应用程序的Shell:
<Window ..........>
<Grid>
<ContentControl
prism:RegionManager.RegionName="{x:Static inf:RegionNames.ContentRegion}" />
</Grid>
</Window>
这里ContentRegion只是在另一类基础设施项目中定义的静态字符串。
这是我的Bootstrapper类:
public class Bootstrapper : MefBootstrapper
{
protected override DependencyObject CreateShell()
{
return Container.GetExportedValue<Shell>();
}
protected override void InitializeShell()
{
base.InitializeShell();
App.Current.MainWindow = (Window)Shell;
App.Current.MainWindow.Show();
}
protected override void ConfigureAggregateCatalog()
{
AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(Bootstrapper).Assembly));
AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(RegionNames).Assembly));
AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(ModuleMyModule).Assembly));
}
}
如您所见,我已将主要执行项目及其基础结构项目添加到此Bootstrapper。
现在我创建了一个名为MyModule的非常简单的模块。 它有一个名为ModuleMyModule的类:
[ModuleExport(typeof(ModuleMyModule), InitializationMode = InitializationMode.WhenAvailable)]
[PartCreationPolicy(CreationPolicy.NonShared)]
public class ModuleMyModule : IModule
{
IRegionManager _regionManager;
[ImportingConstructor]
public ModuleMyModule(IRegionManager regionManager)
{
_regionManager = regionManager;
}
public void Initialize()
{
_regionManager.RegisterViewWithRegion(RegionNames.ContentRegion, typeof(MyView));
}
}
现在,我在这个应用程序中有一个名为MyView的View,如下所示:
<UserControl ............>
<Grid>
<CheckBox Content="Have you Checked it properly?"/>
</Grid>
</UserControl>
到目前为止,我的应用程序运行良好。
问题现在就开始了:
现在,我在这个项目中添加了一个ViewModel。所以,现在我的视图MyView看起来像:
<UserControl ............>
<Grid>
<CheckBox IsChecked="{Binding IsProperlyChecked}" Content="Have you Checked it properly?"/>
</Grid>
</UserControl>
以下是MyView的.cs文件:
[Export(typeof(MyView))]
[PartCreationPolicy(CreationPolicy.NonShared)]
public partial class MyView : UserControl, IView
{
[ImportingConstructor]
public MyView(IMyViewModel viewModel)
{
InitializeComponent();
ViewModel = viewModel;
}
public IViewModel ViewModel
{
get
{
return (IViewModel)DataContext;
}
set
{
DataContext = value;
}
}
}
这是我的ViewModel类:
[Export(typeof(MyViewModel))]
[PartCreationPolicy(CreationPolicy.NonShared)]
public class MyViewModel : IMyViewModel, INotifyPropertyChanged
{
[ImportingConstructor]
public MyViewModel()
{
IsProperlyChecked = true;
}
private bool _IsProperlyChecked;
public bool IsProperlyChecked
{
get
{
return _IsProperlyChecked;
}
set
{
if (_IsProperlyChecked != value)
{
_IsProperlyChecked = value;
OnPropertyChanged("IsProperlyChecked");
}
}
}
public void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
IMyViewModel是一个界面,如下所示:
public interface IMyViewModel : IViewModel
{
bool IsProperlyChecked { get; set; }
}
现在,我的项目停止了工作:
我收到错误:
An exception has occurred while trying to add a view to region 'ContentRegion'.
- The most likely causing exception was was: 'Microsoft.Practices.ServiceLocation.ActivationException: Activation error occured while trying to get instance of type MyView, key "" ---> Microsoft.Practices.ServiceLocation.ActivationException: Activation error occured while trying to get instance of type MyView, key ""
at Microsoft.Practices.Prism.MefExtensions.MefServiceLocatorAdapter.DoGetInstance(Type serviceType, String key)
at Microsoft.Practices.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType, String key)
--- End of inner exception stack trace ---
at Microsoft.Practices.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType, String key)
at Microsoft.Practices.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType)
at Microsoft.Practices.Prism.Regions.RegionViewRegistry.CreateInstance(Type type)
at Microsoft.Practices.Prism.Regions.RegionViewRegistry.<>c__DisplayClass1.<RegisterViewWithRegion>b__0()
at Microsoft.Practices.Prism.Regions.Behaviors.AutoPopulateRegionBehavior.OnViewRegistered(Object sender, ViewRegisteredEventArgs e)'.
为什么抛出这个异常?
我认为我做错了什么。我对MEF很新,我过去使用过Unity。
我需要注册ViewModel及其界面。但我不知道MEF中是否需要它。如果需要那么How ???
演示项目:
https://drive.google.com/file/d/0Bw2XAE1EBI6rU3VsYjVyQmhFRFE/view?usp=sharing
答案 0 :(得分:4)
使用MEF时,ExportAttribute
中作为参数传递的类型应与导入所需的类型匹配。
由于MyView
构造函数需要IMyViewModel
类型:
[ImportingConstructor]
public MyView(IMyViewModel viewModel)
{
..
...尝试将MyViewModel类导出为IMyViewModel
[Export(typeof(IMyViewModel))]
[PartCreationPolicy(CreationPolicy.NonShared)]
public class MyViewModel : IMyViewModel, INotifyPropertyChanged
{
...