检索实现给定接口的对象列表 [英] Retrieve a list of object implementing a given interface

问题描述

简介

我正在我的应用程序中构建插件架构.插件实现给定的接口IBasePlugin，或从基本接口继承的其他接口:

I am building a plugin architecture in my app. The plugins implement a given Interface IBasePlugin, or some other interface which inherited from the base interface:

interface IBasePlugin
interface IMainFormEvents : IBasePlugin

宿主正在加载插件程序集，然后创建实现 IBasePlugin 接口的任何类的适当对象..

The host is loading the plugin assemblies, and then creates the appropriate object of any class implementing the IBasePlugin interface..

这是加载插件和实例化对象的类:

This is the class loading the plugins and instantiating the objects:

 public class PluginCore
 {
     #region implement singletone instance of class
     private static PluginCore instance;
     public static PluginCore PluginCoreSingleton
     {
         get
         {
             if (instance == null)
             {
                 instance = new PluginCore();
             }
             return instance;
         }
     }
     #endregion

     private List<Assembly> _PlugInAssemblies = null;
     /// <summary>
     /// Gets the plug in assemblies.
     /// </summary>
     /// <value>The plug in assemblies.</value>
     public List<Assembly> PlugInAssemblies
     {
         get
         {
             if (_PlugInAssemblies != null) return _PlugInAssemblies;

             // Load Plug-In Assemblies
             DirectoryInfo dInfo = new DirectoryInfo(
                 Path.Combine(
                     Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location),
                     "Plugins"
                     )
                 );
             FileInfo[] files = dInfo.GetFiles("*.dll");
             _PlugInAssemblies = new List<Assembly>();
             if (null != files)
             {
                 foreach (FileInfo file in files)
                 {
                     _PlugInAssemblies.Add(Assembly.LoadFile(file.FullName));
                 }
             }

             return _PlugInAssemblies;
         }
     }

     List<IBasePlugin> _pluginsList = null;
     /// <summary>
     /// Gets the plug ins instances.
     /// all the plugins are being instanciated ONCE when this if called for the first time
     /// every other call will return the existing classes.
     /// </summary>
     /// <value>The plug ins instances.</value>
     public List<IBasePlugin> PlugInInstances
     {
         get
         {
             if (_pluginsList != null) return _pluginsList;

             List<Type> availableTypes = new List<Type>();

             foreach (Assembly currentAssembly in this.PlugInAssemblies)
                 availableTypes.AddRange(currentAssembly.GetTypes());

             // get a list of objects that implement the IBasePlugin
             List<Type> pluginsList = availableTypes.FindAll(delegate(Type t)
             {
                 List<Type> interfaceTypes = new List<Type>(t.GetInterfaces());
                 return interfaceTypes.Contains(typeof(IBasePlugin));
             });

             // convert the list of Objects to an instantiated list of IBasePlugin
             _pluginsList = pluginsList.ConvertAll<IBasePlugin>(delegate(Type t) { return Activator.CreateInstance(t) as IBasePlugin; });

             return _pluginsList;
         }
     }

问题

目前，任何支持插件的模块都使用 PlugInInstances 属性来检索 IBasePlugins 列表.然后它迭代查询谁在实现给定子接口的对象.

Currently, any module which supports the plugins, uses the PlugInInstances property to retrieve the IBasePlugins list. Then it iterates the objects querying who is implementing a given child interface.

foreach (IBasePlugin plugin in PluginCore.PluginCoreSingleton.PlugInInstances)
{
     if (plugin is IMainFormEvents)
     {
         // Do something
     }
 }

我想改进这项技术，让函数接收给定的子接口，并返回这些接口的列表.问题是不应在调用者中进行转换.

I would like to improve this technique by having a function that receives a given child interface, and return a list of those interface. The catch is that no casting should be done in the caller.

伪代码:

void GetListByInterface(Type InterfaceType, out List<InterfaceType> Plugins)

您有关于如何实施的建议吗?

Do you have a recommendation on how to implement this?

推荐答案

你可以试试这样的:

void GetListByInterface<TInterface>(out IList<TInterface> plugins) where TInterface : IBasePlugin
{
  plugins = (from p in _allPlugins where p is TInterface select (TInterface)p).ToList();
}

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