MEF 通用框架

internal class Program : IPartImportsSatisfiedNotification
{
    private static void Main(string[] args)
    {
        var mefs = new CommonPartsManager<IMefInterface>();
        mefs.Run();
        var demo = mefs.GetClass("2");
        demo.Send("456778899");

        Console.WriteLine("按任意键退出..............");
        Console.ReadKey();
    }

    public void OnImportsSatisfied()
    {
        throw new NotImplementedException();
    }
}

部件接口

/// <summary>
/// 部件统一接口
/// </summary>
public interface IMefInterface
{
    void Send(string msg);
}
/// <summary>
/// 部件描述类
/// </summary>
public interface IMefInterfaceDepict
{
    string Depict { get; }
}

派生类

// Export标记需要导出的接口类部件
[Export(typeof(IMefInterface))]
[ExportMetadata("Depict", "1")]
public class DemoOneInherit1 : IMefInterface, IDisposable
{
    public void Dispose()
    {
        // release
    }

    public void Send(string msg)
    {
        Console.WriteLine("DemoOneInherit1 send {0}", msg);
    }
}
[Export(typeof(IMefInterface))]
[ExportMetadata("Depict", "2")]
public class DemoOneInherit2 : IMefInterface, IDisposable
{
    public void Dispose()
    {
        // release
    }

    public void Send(string msg)
    {
        Console.WriteLine("DemoOneInherit2 send {0}", msg);
    }
}
[Export(typeof(IMefInterface))]
[ExportMetadata("Depict", "3")]
public class DemoOneInherit3 : IMefInterface, IDisposable
{
    public void Dispose()
    {
        // release
    }

    public void Send(string msg)
    {
        Console.WriteLine("DemoOneInherit3 send {0}", msg);
    }
}

部件管理类

/// <summary>
/// 部件管理类
/// </summary>
/// <typeparam name="T">部件接口类型</typeparam>
public class CommonPartsManager<T>
{
    public CommonPartsManager()
    {
        this.ComposePartsSelf();
    }
    // Import标记需要导入的对象
    [ImportMany(AllowRecomposition = true)]
    private IEnumerable<Lazy<IMefInterface, IMefInterfaceDepict>> _mefs = null;

    /// <summary>
    /// 通过名称反射出对应的类
    /// </summary>
    /// <param name="depictName">部件描述</param>
    /// <returns></returns>
    public T GetClass(string depictName)
    {
        if (Names.Any(x => x == depictName))
        {
            var rslt = _mefs.Where(x => x.Metadata.Depict == depictName).Select(p => p.Value).FirstOrDefault();
            return (T)rslt;
        }
        return default;
    }

    /// <summary>
    /// 部件名称
    /// </summary>
    public IEnumerable<string> Names
    {
        get => _mefs.Select(x => x.Metadata.Depict);
    }

    // test
    public void Run()
    {
        foreach (var item in _mefs)
        {
            item.Value.Send($"DemoOne.Run {item.Metadata.Depict}");
        }
    }
}

MEF扩展

public static partial class ObjectExt
{
    /// <summary>
    /// 自定义组合部件
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="obj"></param>
    /// <returns></returns>
    public static T ComposePartsSelf<T>(this T obj, string dirName = ".") where T : class
    {
        var cataLog = new AggregateCatalog();
        // 在程序集中查找目录
        cataLog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));
        // 在路径中查找
        cataLog.Catalogs.Add(new DirectoryCatalog(dirName)); //遍历运行目录下的文件夹，查找所需的插件
        // 加载指定模块
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(DemoOneInherit3 ).Assembly));
        var container = new CompositionContainer(cataLog);
        try
        {
            container.ComposeParts(obj);
        }
        catch (CompositionException ex)
        {
            Console.WriteLine(ex.ToString());
        }

        return obj;
    }
    /// <summary>
    /// 对目录中部件的筛选
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="obj"></param>
    /// <param name="dirName"></param>
    /// <param name="metadataKey"></param>
    /// <param name="metadataValue"></param>
    /// <returns></returns>
    public static T ComposePartsFilter<T>(this T obj, string dirName = ".", string metadataKey = "", string metadataValue = "") where T : class
    {
        var cataLog = new AggregateCatalog();
        // 在程序集中查找目录
        cataLog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));
        // 在路径中查找
        cataLog.Catalogs.Add(new DirectoryCatalog(dirName)); //遍历运行目录下的文件夹，查找所需的插件
        var containerParent = new CompositionContainer(cataLog);

        var filteredCat = new FilteredCatalog(cataLog, def =>
          def.Metadata.ContainsKey(metadataKey) &&
        def.Metadata[metadataKey].ToString() == metadataValue);
        var preRequest = new CompositionContainer(filteredCat, containerParent);
        try
        {
            preRequest.ComposeParts(obj);
        }
        catch (CompositionException ex)
        {
            Console.WriteLine(ex.ToString());
        }

        return obj;
    }
}
/// <summary>
/// 目录筛选
/// </summary>
public class FilteredCatalog : ComposablePartCatalog, INotifyComposablePartCatalogChanged
{
    private readonly ComposablePartCatalog _inner;
    private readonly INotifyComposablePartCatalogChanged _innerNotifyChange;
    private readonly IQueryable<ComposablePartDefinition> _partsQuery;
    public FilteredCatalog(ComposablePartCatalog inner, Expression<Func<ComposablePartDefinition, bool>> expression)
    {
        _inner = inner;
        _innerNotifyChange = inner as INotifyComposablePartCatalogChanged;
        _partsQuery = inner.Parts.Where(expression);
    }
    public event EventHandler<ComposablePartCatalogChangeEventArgs> Changed
    {
        add
        {
            if (_innerNotifyChange != null)
            {
                _innerNotifyChange.Changed += value;
            }
        }
        remove
        {
            if (_innerNotifyChange != null)
            {
                _innerNotifyChange.Changed -= value;
            }
        }
    }
    public event EventHandler<ComposablePartCatalogChangeEventArgs> Changing
    {
        add
        {
            if (_innerNotifyChange != null)
            {
                _innerNotifyChange.Changing += value;
            }
        }
        remove
        {
            if (_innerNotifyChange != null)
            {
                _innerNotifyChange.Changing -= value;
            }
        }
    }
    public override IQueryable<ComposablePartDefinition> Parts => _partsQuery;

}