之前一直使用 MvvmLight 进行相关的 WPF 开发工作，插件式开发还是在 2 年前接触到 Prism 框架后才真正实践过，由于 Prism 本身太重，不太适合新人入门，我当初也是理解了好久一段时间。 这两天又看了一下 MEF 的相关东西，发现理解起来顺畅多了，于是分别写了一个简易版的 Demo 练一下手
- 通过 IOC 和 DI 方式将服务和模块导出和动态加载
- 通过使用 MvvmLight 的 MessengerInstance 实现模块间通信
- 主程序：Sample
public partial class MainView : Window
{
[ImportMany(typeof(IView))]
public Lazy<IView, IMetadata>[] Plugins { get; private set; }
private CompositionContainer container = null;
public MainView()
{
InitializeComponent();
var dir = new DirectoryInfo(Path.Combine(Environment.CurrentDirectory, "Plugins"));
if (dir.Exists)
{
var catalog = new DirectoryCatalog(dir.FullName, "Sample.*.dll");
container = new CompositionContainer(catalog);
container.ComposeParts(this);
Plugins.OrderBy(p => p.Metadata.Priority);
foreach (var item in Plugins)
{
this.tab.Items.Add(new TabItem()
{
Header = item.Metadata.Name,
Content = item.Value
});
}
}
}
protected override void OnClosing(CancelEventArgs e)
{
container?.Dispose();
base.OnClosing(e);
}
}- 强类型元数据接口及相关实现
public interface IMetadata
{
[DefaultValue(0)]
int Priority { get; }
string Name { get; }
string Description { get; }
string Author { get; }
string Version { get; }
}
[MetadataAttribute]
[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
public class CustomExportMetadata : ExportAttribute, IMetadata
{
public int Priority { get; private set; }
public string Name { get; private set; }
public string Description { get; private set; }
public string Author{ get; private set; }
public string Version { get; private set; }
public CustomExportMetadata() : base(typeof(IMetadata))
{
}
public CustomExportMetadata(int priority):this()
{
this.Priority = priority;
}
public CustomExportMetadata(int priority, string name) : this(priority)
{
this.Name = name;
}
public CustomExportMetadata(int priority, string name, string description) : this(priority, name)
{
this.Description = description;
}
public CustomExportMetadata(int priority, string name, string description, string author) : this(priority, name, description)
{
this.Author = author;
}
public CustomExportMetadata(int priority, string name, string description, string author, string version) : this(priority, name, description, author)
{
this.Version = version;
}
}- 子模块 1：Sample.Plugin1
[Export(typeof(IView))]
[CustomExportMetadata(0, "Plugin1")]
public partial class MainView : UserControl, IView
{
[ImportingConstructor]
public MainView([Import("DataService")]IService service)
{
this.DataContext = new MainViewModel(service);
InitializeComponent();
}
}- 子模块 2：Sample.Plugin2
[Export(typeof(IView))]
[CustomExportMetadata(1, "Plugin2")]
public partial class MainView : UserControl, IView
{
public MainView()
{
this.DataContext = new MainViewModel();
InitializeComponent();
}
}- EMF
- 延迟加载
- 元数据（强类型）导出
- MVVM
- 模块通信
- 样式共享
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