TypeFinder学习

不知道大家是如何查找反射程序集中的类型。Nop封装了一个不错的实现。

接口ITypeFinder

/// <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);

        IEnumerable<Type> FindClassesOfType<T, TAssemblyAttribute>(bool onlyConcreteClasses = true) where TAssemblyAttribute : Attribute;

        IEnumerable<Assembly> FindAssembliesWithAttribute<T>();

        IEnumerable<Assembly> FindAssembliesWithAttribute<T>(IEnumerable<Assembly> assemblies);

        IEnumerable<Assembly> FindAssembliesWithAttribute<T>(DirectoryInfo assemblyPath);


    }

Nop中的三个ITypeFinder实现类。

1.FakeTypeFinder

模拟额TypeFinder，通过构造器传递模拟需要查找的类型

[Test]
        public void MyFakeTypeFinder()
        {
            var finder = new FakeTypeFinder(typeof(SomeClass));

            var type = finder.FindClassesOfType<ISomeInterface>();
            Assert.True(type.Any());
        }

        public interface ISomeInterface
        {
        }

        public class SomeClass : ISomeInterface
        {
        }

2.AppDomainTypeFinder，在App或者单元测试中使用

[Test]
        public void TypeFinder_Benchmark_Findings()
        {
            var finder = new AppDomainTypeFinder();
            var type = finder.FindClassesOfType<ISomeInterface>();
            type.Count().ShouldEqual(1);
            typeof(ISomeInterface).IsAssignableFrom(type.FirstOrDefault()).ShouldBeTrue();
        }

3.WebAppTypeFinder

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

那TypeFinder是如何工作的？

1.FakeType（查找通过构造函数传递进来的types中的类型）

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

2.AppDomainTypeFinder(匹配循环程序集中的类)

public IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true)
        {
            var result = new List<Type>();
            try
            {
                foreach (var a in assemblies)
                {
                    foreach (var t in a.GetTypes())
                    {
                        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;
        }

总结：TypeFinder提供了简便的接口来查找程序集中的类。我们也可以很方便的提取出来使用在自己的项目中。