这对我很管用。它循环遍历这些类并检查它们是否派生自myInterface

 foreach (Type mytype in System.Reflection.Assembly.GetExecutingAssembly().GetTypes()
                 .Where(mytype => mytype .GetInterfaces().Contains(typeof(myInterface)))) {
    //do stuff
 }

查找程序集中实现IFoo接口的所有类型:

var results = from type in someAssembly.GetTypes()
              where typeof(IFoo).IsAssignableFrom(type)
              select type;

请注意Ryan Rinaldi的建议是不正确的。它将返回0个类型。你不能写字

where type is IFoo

因为类型是一个系统。类型实例，并且永远不会是IFoo类型。相反，检查IFoo是否可以从类型中赋值。这将得到你预期的结果。

此外，亚当·赖特的建议，目前被标记为答案，也是不正确的，出于同样的原因。在运行时，您将看到返回0类型，因为所有System。类型实例不是IFoo实现者。

你可以使用一些LINQ来获取列表:

var types = from type in this.GetType().Assembly.GetTypes()
            where type is ISomeInterface
            select type;

但说真的，这样更有可读性吗?

我知道这是一个非常老的问题，但我想我将为未来的用户添加另一个答案，因为迄今为止所有的答案都使用某种形式的Assembly.GetTypes。

虽然GetTypes()确实会返回所有类型，但这并不一定意味着您可以激活它们，从而可能会抛出一个reflectiontypeloadeexception异常。

无法激活类型的典型示例是，当返回的类型是从base派生的，但base定义在与派生的不同的程序集中，调用程序集没有引用该程序集。

假设我们有:

Class A // in AssemblyA
Class B : Class A, IMyInterface // in AssemblyB
Class C // in AssemblyC which references AssemblyB but not AssemblyA

如果在AssemblyC中的ClassC中，我们按照接受的答案做一些事情:

var type = typeof(IMyInterface);
var types = AppDomain.CurrentDomain.GetAssemblies()
    .SelectMany(s => s.GetTypes())
    .Where(p => type.IsAssignableFrom(p));

然后它将抛出一个reflectiontypeloadeexception异常。

这是因为在AssemblyC中没有对AssemblyA的引用，您将无法:

var bType = typeof(ClassB);
var bClass = (ClassB)Activator.CreateInstance(bType);

换句话说，ClassB是不可加载的这是GetTypes调用检查并抛出的东西。

因此，为了安全地限定结果集为可加载类型，然后根据Phil haked的文章在一个程序集中获取所有类型和Jon Skeet代码，你会做这样的事情:

public static class TypeLoaderExtensions {
    public static IEnumerable<Type> GetLoadableTypes(this Assembly assembly) {
        if (assembly == null) throw new ArgumentNullException("assembly");
        try {
            return assembly.GetTypes();
        } catch (ReflectionTypeLoadException e) {
            return e.Types.Where(t => t != null);
        }
    }
}

然后:

private IEnumerable<Type> GetTypesWithInterface(Assembly asm) {
    var it = typeof (IMyInterface);
    return asm.GetLoadableTypes().Where(it.IsAssignableFrom).ToList();
}

我的是c# 3.0:)

var type = typeof(IMyInterface);
var types = AppDomain.CurrentDomain.GetAssemblies()
    .SelectMany(s => s.GetTypes())
    .Where(p => type.IsAssignableFrom(p));

基本上，最少的迭代次数总是:

loop assemblies  
 loop types  
  see if implemented.

已经有许多有效的答案，但我想添加另一个实现作为类型扩展和一个单元测试列表，以演示不同的场景:

public static class TypeExtensions
{
    public static IEnumerable<Type> GetAllTypes(this Type type)
    {
        var typeInfo = type.GetTypeInfo();
        var allTypes = GetAllImplementedTypes(type).Concat(typeInfo.ImplementedInterfaces);
        return allTypes;
    }

    private static IEnumerable<Type> GetAllImplementedTypes(Type type)
    {
        yield return type;
        var typeInfo = type.GetTypeInfo();
        var baseType = typeInfo.BaseType;
        if (baseType != null)
        {
            foreach (var foundType in GetAllImplementedTypes(baseType))
            {
                yield return foundType;
            }
        }
    }
}

该算法支持以下场景:

public static class GetAllTypesTests
{
    public class Given_A_Sample_Standalone_Class_Type_When_Getting_All_Types
        : Given_When_Then_Test
    {
        private Type _sut;
        private IEnumerable<Type> _expectedTypes;
        private IEnumerable<Type> _result;

        protected override void Given()
        {
            _sut = typeof(SampleStandalone);

            _expectedTypes =
                new List<Type>
                {
                    typeof(SampleStandalone),
                    typeof(object)
                };
        }

        protected override void When()
        {
            _result = _sut.GetAllTypes();
        }

        [Fact]
        public void Then_It_Should_Return_The_Right_Type()
        {
            _result.Should().BeEquivalentTo(_expectedTypes);
        }
    }

    public class Given_A_Sample_Abstract_Base_Class_Type_When_Getting_All_Types
        : Given_When_Then_Test
    {
        private Type _sut;
        private IEnumerable<Type> _expectedTypes;
        private IEnumerable<Type> _result;

        protected override void Given()
        {
            _sut = typeof(SampleBase);

            _expectedTypes =
                new List<Type>
                {
                    typeof(SampleBase),
                    typeof(object)
                };
        }

        protected override void When()
        {
            _result = _sut.GetAllTypes();
        }

        [Fact]
        public void Then_It_Should_Return_The_Right_Type()
        {
            _result.Should().BeEquivalentTo(_expectedTypes);
        }
    }

    public class Given_A_Sample_Child_Class_Type_When_Getting_All_Types
        : Given_When_Then_Test
    {
        private Type _sut;
        private IEnumerable<Type> _expectedTypes;
        private IEnumerable<Type> _result;

        protected override void Given()
        {
            _sut = typeof(SampleChild);

            _expectedTypes =
                new List<Type>
                {
                    typeof(SampleChild),
                    typeof(SampleBase),
                    typeof(object)
                };
        }

        protected override void When()
        {
            _result = _sut.GetAllTypes();
        }

        [Fact]
        public void Then_It_Should_Return_The_Right_Type()
        {
            _result.Should().BeEquivalentTo(_expectedTypes);
        }
    }

    public class Given_A_Sample_Base_Interface_Type_When_Getting_All_Types
        : Given_When_Then_Test
    {
        private Type _sut;
        private IEnumerable<Type> _expectedTypes;
        private IEnumerable<Type> _result;

        protected override void Given()
        {
            _sut = typeof(ISampleBase);

            _expectedTypes =
                new List<Type>
                {
                    typeof(ISampleBase)
                };
        }

        protected override void When()
        {
            _result = _sut.GetAllTypes();
        }

        [Fact]
        public void Then_It_Should_Return_The_Right_Type()
        {
            _result.Should().BeEquivalentTo(_expectedTypes);
        }
    }

    public class Given_A_Sample_Child_Interface_Type_When_Getting_All_Types
        : Given_When_Then_Test
    {
        private Type _sut;
        private IEnumerable<Type> _expectedTypes;
        private IEnumerable<Type> _result;

        protected override void Given()
        {
            _sut = typeof(ISampleChild);

            _expectedTypes =
                new List<Type>
                {
                    typeof(ISampleBase),
                    typeof(ISampleChild)
                };
        }

        protected override void When()
        {
            _result = _sut.GetAllTypes();
        }

        [Fact]
        public void Then_It_Should_Return_The_Right_Type()
        {
            _result.Should().BeEquivalentTo(_expectedTypes);
        }
    }

    public class Given_A_Sample_Implementation_Class_Type_When_Getting_All_Types
        : Given_When_Then_Test
    {
        private Type _sut;
        private IEnumerable<Type> _expectedTypes;
        private IEnumerable<Type> _result;

        protected override void Given()
        {
            _sut = typeof(SampleImplementation);

            _expectedTypes =
                new List<Type>
                {
                    typeof(SampleImplementation),
                    typeof(SampleChild),
                    typeof(SampleBase),
                    typeof(ISampleChild),
                    typeof(ISampleBase),
                    typeof(object)
                };
        }

        protected override void When()
        {
            _result = _sut.GetAllTypes();
        }

        [Fact]
        public void Then_It_Should_Return_The_Right_Type()
        {
            _result.Should().BeEquivalentTo(_expectedTypes);
        }
    }

    public class Given_A_Sample_Interface_Instance_Type_When_Getting_All_Types
        : Given_When_Then_Test
    {
        private Type _sut;
        private IEnumerable<Type> _expectedTypes;
        private IEnumerable<Type> _result;

        class Foo : ISampleChild { }

        protected override void Given()
        {
            var foo = new Foo();
            _sut = foo.GetType();

            _expectedTypes =
                new List<Type>
                {
                    typeof(Foo),
                    typeof(ISampleChild),
                    typeof(ISampleBase),
                    typeof(object)
                };
        }

        protected override void When()
        {
            _result = _sut.GetAllTypes();
        }

        [Fact]
        public void Then_It_Should_Return_The_Right_Type()
        {
            _result.Should().BeEquivalentTo(_expectedTypes);
        }
    }

    sealed class SampleStandalone { }
    abstract class SampleBase { }
    class SampleChild : SampleBase { }
    interface ISampleBase { }
    interface ISampleChild : ISampleBase { }
    class SampleImplementation : SampleChild, ISampleChild { }
}