类型查找器 ITypeFinder

 NopCommerce为了支持插件功能，以及支持一些自动注册的功能。系统提供了类型查找器。ITypeFinder以及实现类就是提供此功能。通过类型查找器可以查找本程序域中的类，也可以查找整个bin目录下所有动态链接库中类，并把它们注册到类型反转容器中。ITypeFinder以及实现类如下：

ITypeFinder接口

/// <summary>
    /// Classes implementing this interface provide information about types 
    /// to various services in the Nop engine.
    /// </summary>
    public interface ITypeFinder
    {
        IList<Assembly> GetAssemblies();

        IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, bool onlyConcreteClasses = true);

        IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true);

        IEnumerable<Type> FindClassesOfType<T>(bool onlyConcreteClasses = true);

        IEnumerable<Type> FindClassesOfType<T>(IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true);
    }

FakeTypeFinder(模拟类型查找器)

 /// <summary>
    /// 模拟类型查找
    /// </summary>
    public class FakeTypeFinder : ITypeFinder
    {
        public Assembly[] Assemblies { get; set; }
        public Type[] Types { get; set; }

        public FakeTypeFinder(Assembly assembly, params Type[] types)
        {
            Assemblies = new[] { assembly };
            this.Types = types;
        }
        public FakeTypeFinder(params Type[] types)
        {
            Assemblies = new Assembly[0];
            this.Types = types;
        }
        public FakeTypeFinder(params Assembly[] assemblies)
        {
            this.Assemblies = assemblies;
        }

        public IList<Assembly> GetAssemblies()
        {
            return Assemblies.ToList();
        }



        public IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, bool onlyConcreteClasses = true)
        {
            return (from t in Types
                    where !t.IsInterface && assignTypeFrom.IsAssignableFrom(t) && (onlyConcreteClasses ? (t.IsClass && !t.IsAbstract) : true)
                    select t).ToList();
        }

        public IEnumerable<Type> FindClassesOfType<T>(bool onlyConcreteClasses = true)
        {
            return FindClassesOfType(typeof(T), onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true)
        {
            return FindClassesOfType(assignTypeFrom, onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType<T>(IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true)
        {
            return FindClassesOfType(typeof(T), onlyConcreteClasses);
        }
    }

 #region FakeTypeFinder

        [TestMethod]
        public void FakeTypeFinderTest()
        {
            var finder = new FakeTypeFinder(typeof(FakeClass));
            var type = finder.FindClassesOfType<IFakeInterface>();
            Assert.IsTrue(type.Any());
        }
        public interface IFakeInterface
        {
        }
        public class FakeClass : IFakeInterface
        {
        }

        #endregion

AppDomainTypeFinder(应用程序类型查找器)

/// <summary>
    /// A class that finds types needed by Nop by looping assemblies in the 
    /// currently executing AppDomain. Only assemblies whose names matches
    /// certain patterns are investigated and an optional list of assemblies
    /// referenced by <see cref="AssemblyNames"/> are always investigated.
    /// </summary>
    public class AppDomainTypeFinder : ITypeFinder
    {
        #region Fields

        private bool ignoreReflectionErrors = true;
        private bool loadAppDomainAssemblies = true;
        private string assemblySkipLoadingPattern = "^System|^mscorlib|^Microsoft|^AjaxControlToolkit|^Antlr3|^Autofac|^AutoMapper|^Castle|^ComponentArt|^CppCodeProvider|^DotNetOpenAuth|^EntityFramework|^EPPlus|^FluentValidation|^ImageResizer|^itextsharp|^log4net|^MaxMind|^MbUnit|^MiniProfiler|^Mono.Math|^MvcContrib|^Newtonsoft|^NHibernate|^nunit|^Org.Mentalis|^PerlRegex|^QuickGraph|^Recaptcha|^Remotion|^RestSharp|^Rhino|^Telerik|^Iesi|^TestDriven|^TestFu|^UserAgentStringLibrary|^VJSharpCodeProvider|^WebActivator|^WebDev|^WebGrease";
        private string assemblyRestrictToLoadingPattern = ".*";
        private IList<string> assemblyNames = new List<string>();

        #endregion

        #region Properties

        /// <summary>The app domain to look for types in.</summary>
        public virtual AppDomain App
        {
            get { return AppDomain.CurrentDomain; }
        }

        /// <summary>Gets or sets wether Nop should iterate assemblies in the app domain when loading Nop types. Loading patterns are applied when loading these assemblies.</summary>
        public bool LoadAppDomainAssemblies
        {
            get { return loadAppDomainAssemblies; }
            set { loadAppDomainAssemblies = value; }
        }

        /// <summary>Gets or sets assemblies loaded a startup in addition to those loaded in the AppDomain.</summary>
        public IList<string> AssemblyNames
        {
            get { return assemblyNames; }
            set { assemblyNames = value; }
        }

        /// <summary>Gets the pattern for dlls that we know don't need to be investigated.</summary>
        public string AssemblySkipLoadingPattern
        {
            get { return assemblySkipLoadingPattern; }
            set { assemblySkipLoadingPattern = value; }
        }

        /// <summary>Gets or sets the pattern for dll that will be investigated. For ease of use this defaults to match all but to increase performance you might want to configure a pattern that includes assemblies and your own.</summary>
        /// <remarks>If you change this so that Nop assemblies arn't investigated (e.g. by not including something like "^Nop|..." you may break core functionality.</remarks>
        public string AssemblyRestrictToLoadingPattern
        {
            get { return assemblyRestrictToLoadingPattern; }
            set { assemblyRestrictToLoadingPattern = value; }
        }

        #endregion

        #region Methods

        public IEnumerable<Type> FindClassesOfType<T>(bool onlyConcreteClasses = true)
        {
            return FindClassesOfType(typeof(T), onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, bool onlyConcreteClasses = true)
        {
            return FindClassesOfType(assignTypeFrom, GetAssemblies(), onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType<T>(IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true)
        {
            return FindClassesOfType(typeof (T), assemblies, onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true)
        {
            var result = new List<Type>();
            try
            {
                foreach (var a in assemblies)
                {
                    Type[] types = null;
                    try
                    {
                        types = a.GetTypes();
                    }
                    catch
                    {
                        //Entity Framework 6 doesn't allow getting types (throws an exception)
                        if (!ignoreReflectionErrors)
                        {
                            throw;
                        }
                    }
                    if (types != null)
                    {
                        foreach (var t in types)
                        {
                            if (assignTypeFrom.IsAssignableFrom(t) || (assignTypeFrom.IsGenericTypeDefinition && DoesTypeImplementOpenGeneric(t, assignTypeFrom)))
                            {
                                if (!t.IsInterface)
                                {
                                    if (onlyConcreteClasses)
                                    {
                                        if (t.IsClass && !t.IsAbstract)
                                        {
                                            result.Add(t);
                                        }
                                    }
                                    else
                                    {
                                        result.Add(t);
                                    }
                                }
                            }
                        }
                    }
                }
            }
            catch (ReflectionTypeLoadException ex)
            {
                var msg = string.Empty;
                foreach (var e in ex.LoaderExceptions)
                    msg += e.Message + Environment.NewLine;

                var fail = new Exception(msg, ex);
                Debug.WriteLine(fail.Message, fail);

                throw fail;
            }
            return result;
        }

        /// <summary>Gets the assemblies related to the current implementation.</summary>
        /// <returns>A list of assemblies that should be loaded by the Nop factory.</returns>
        public virtual IList<Assembly> GetAssemblies()
        {
            var addedAssemblyNames = new List<string>();
            var assemblies = new List<Assembly>();

            if (LoadAppDomainAssemblies)
                AddAssembliesInAppDomain(addedAssemblyNames, assemblies);
            AddConfiguredAssemblies(addedAssemblyNames, assemblies);

            return assemblies;
        }

        #endregion

        #region Utilities

        /// <summary>
        /// Iterates all assemblies in the AppDomain and if it's name matches the configured patterns add it to our list.
        /// </summary>
        /// <param name="addedAssemblyNames"></param>
        /// <param name="assemblies"></param>
        private void AddAssembliesInAppDomain(List<string> addedAssemblyNames, List<Assembly> assemblies)
        {
            foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
            {
                if (Matches(assembly.FullName))
                {
                    if (!addedAssemblyNames.Contains(assembly.FullName))
                    {
                        assemblies.Add(assembly);
                        addedAssemblyNames.Add(assembly.FullName);
                    }
                }
            }
        }

        /// <summary>
        /// Adds specificly configured assemblies.
        /// </summary>
        /// <param name="addedAssemblyNames"></param>
        /// <param name="assemblies"></param>
        protected virtual void AddConfiguredAssemblies(List<string> addedAssemblyNames, List<Assembly> assemblies)
        {
            foreach (string assemblyName in AssemblyNames)
            {
                Assembly assembly = Assembly.Load(assemblyName);
                if (!addedAssemblyNames.Contains(assembly.FullName))
                {
                    assemblies.Add(assembly);
                    addedAssemblyNames.Add(assembly.FullName);
                }
            }
        }

        /// <summary>
        /// Check if a dll is one of the shipped dlls that we know don't need to be investigated.
        /// </summary>
        /// <param name="assemblyFullName">
        /// The name of the assembly to check.
        /// </param>
        /// <returns>
        /// True if the assembly should be loaded into Nop.
        /// </returns>
        public virtual bool Matches(string assemblyFullName)
        {
            return !Matches(assemblyFullName, AssemblySkipLoadingPattern)
                   && Matches(assemblyFullName, AssemblyRestrictToLoadingPattern);
        }

        /// <summary>
        /// Check if a dll is one of the shipped dlls that we know don't need to be investigated.
        /// </summary>
        /// <param name="assemblyFullName">
        /// The assembly name to match.
        /// </param>
        /// <param name="pattern">
        /// The regular expression pattern to match against the assembly name.
        /// </param>
        /// <returns>
        /// True if the pattern matches the assembly name.
        /// </returns>
        protected virtual bool Matches(string assemblyFullName, string pattern)
        {
            return Regex.IsMatch(assemblyFullName, pattern, RegexOptions.IgnoreCase | RegexOptions.Compiled);
        }

        /// <summary>
        /// Makes sure matching assemblies in the supplied folder are loaded in the app domain.
        /// </summary>
        /// <param name="directoryPath">
        /// The physical path to a directory containing dlls to load in the app domain.
        /// </param>
        protected virtual void LoadMatchingAssemblies(string directoryPath)
        {
            var loadedAssemblyNames = new List<string>();
            foreach (Assembly a in GetAssemblies())
            {
                loadedAssemblyNames.Add(a.FullName);
            }

            if (!Directory.Exists(directoryPath))
            {
                return;
            }

            foreach (string dllPath in Directory.GetFiles(directoryPath, "*.dll"))
            {
                try
                {
                    var an = AssemblyName.GetAssemblyName(dllPath);
                    if (Matches(an.FullName) && !loadedAssemblyNames.Contains(an.FullName))
                    {
                        App.Load(an);
                    }

                    //old loading stuff
                    //Assembly a = Assembly.ReflectionOnlyLoadFrom(dllPath);
                    //if (Matches(a.FullName) && !loadedAssemblyNames.Contains(a.FullName))
                    //{
                    //    App.Load(a.FullName);
                    //}
                }
                catch (BadImageFormatException ex)
                {
                    Trace.TraceError(ex.ToString());
                }
            }
        }

        /// <summary>
        /// Does type implement generic?
        /// </summary>
        /// <param name="type"></param>
        /// <param name="openGeneric"></param>
        /// <returns></returns>
        protected virtual bool DoesTypeImplementOpenGeneric(Type type, Type openGeneric)
        {
            try
            {
                var genericTypeDefinition = openGeneric.GetGenericTypeDefinition();
                foreach (var implementedInterface in type.FindInterfaces((objType, objCriteria) => true, null))
                {
                    if (!implementedInterface.IsGenericType)
                        continue;

                    var isMatch = genericTypeDefinition.IsAssignableFrom(implementedInterface.GetGenericTypeDefinition());
                    return isMatch;
                }
                return false;
            }catch
            {
                return false;
            }
        }

        #endregion
    }

 #region AppDomainTypeFinder

        public void AppDomainTypeFinderTest()
        {
            var finder = new AppDomainTypeFinder();
            var type = finder.FindClassesOfType<IAppDomainInterface>();
            type.Count();
            typeof(IAppDomainInterface).IsAssignableFrom(type.FirstOrDefault());
        }

        public interface IAppDomainInterface
        {
        }
        public class AppDomainClass : IAppDomainInterface
        {
        }

        #endregion

在App或者单元测试中使用

WebAppTypeFinder(Web应用程序类型查找器)

/// <summary>
    /// Provides information about types in the current web application. 
    /// Optionally this class can look at all assemblies in the bin folder.
    /// </summary>
    public class WebAppTypeFinder : AppDomainTypeFinder
    {
        #region Fields

        private bool _ensureBinFolderAssembliesLoaded = true;
        private bool _binFolderAssembliesLoaded;

        #endregion

        #region Ctor

        public WebAppTypeFinder(NopConfig config)
        {
            this._ensureBinFolderAssembliesLoaded = config.DynamicDiscovery;
        }

        #endregion

        #region Properties

        /// <summary>
        /// Gets or sets wether assemblies in the bin folder of the web application should be specificly checked for beeing loaded on application load. This is need in situations where plugins need to be loaded in the AppDomain after the application been reloaded.
        /// </summary>
        public bool EnsureBinFolderAssembliesLoaded
        {
            get { return _ensureBinFolderAssembliesLoaded; }
            set { _ensureBinFolderAssembliesLoaded = value; }
        }
        
        #endregion

        #region Methods

        /// <summary>
        /// Gets a physical disk path of Bin directory
        /// </summary>
        /// <returns>The physical path. E.g. "c:inetpubwwwrootin"</returns>
        public virtual string GetBinDirectory()
        {
            if (HostingEnvironment.IsHosted)
            {
                //hosted
                return HttpRuntime.BinDirectory;
            }

            //not hosted. For example, run either in unit tests
            return AppDomain.CurrentDomain.BaseDirectory;
        }

        public override IList<Assembly> GetAssemblies()
        {
            if (this.EnsureBinFolderAssembliesLoaded && !_binFolderAssembliesLoaded)
            {
                _binFolderAssembliesLoaded = true;
                string binPath = GetBinDirectory();
                //binPath = _webHelper.MapPath("~/bin");
                LoadMatchingAssemblies(binPath);
            }

            return base.GetAssemblies();
        }

        #endregion
    }

继承自AppDomainTypeFinder。比AppDomainTypeFinder多支持了Web项目的类型查找

WebAppTypeFinder 这个类就可以对网站下面BIN文件夹所有的DLL文件进行反射查找程序集，可以根据类型 也可以跟特性查找，总之性能不错，大家可以拷贝代码 进行测试

http://www.cnblogs.com/miku/archive/2012/09/24/2700776.html

http://www.cnblogs.com/flyfish2012/p/3779810.html