System.Type参数上的ParameterOverride失败

Question

我正在尝试使用ParameterOverrideUnity 2.0.只要我提供的参数不是System.Type,它就可以正常工作.

在下面的测试程序中,MyClass<T>当泛型参数T是int时,我使用整数参数注入构造函数,当T是System.Type时,我使用Type参数.在随后的输出中,您将看到它处理整数就好了,但似乎认为这typeof(MyClassForParam)是一个实际的MyClassForParam对象,而不是类型.有任何想法吗？

namespace UnityParameterOverride
{
    interface IMyClass
    {
    }

    public class MyClass<T> : IMyClass
    {
        public MyClass(T myParam)
        {
            Console.WriteLine("{0}", myParam);
        }
    }

    public class MyClassForParam
    {
        public MyClassForParam() { }
    }

    class Program
    {
        static void Main(string[] args)
        {
            IUnityContainer unity = new UnityContainer();
            try
            {
                // Works fine: prints 12345
                Console.WriteLine("Injecting an integer parameter.");
                unity.RegisterType<IMyClass, MyClass<int>>();
                unity.Resolve<IMyClass>(new ParameterOverride("myParam", 12345));

                // Fails: Seems to think that the parameter is an actual MyClassForParam instead of the type of that class.
                Console.WriteLine();
                Console.WriteLine("Injecting a Type parameter.");
                unity.RegisterType<IMyClass, MyClass<Type>>();
                unity.Resolve<IMyClass>(new ParameterOverride("myParam", typeof(MyClassForParam)));
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.ReadLine();
        }
    }
}

输出如下:

Injecting an integer parameter.
12345

Injecting a Type parameter. ----
Resolution of the dependency failed, type = "UnityParameterOverride.IMyClass", name = "(none)".

发生异常时:

Exception occurred while: Resolving parameter "myParam" of constructor UnityParameterOverride.MyClass`1[[System.Type, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]](System.Type myParam).
Exception is: InvalidCastException - Unable to cast object of type 'UnityParameterOverride.MyClassForParam' to type 'System.Type'.

在例外时,容器是:

Resolving UnityParameterOverride.MyClass1[System.Type],(none) (mapped from Un ityParameterOverride.IMyClass, (none)) Resolving parameter "myParam" of constructor UnityParameterOverride.MyClass1[ [System.Type, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c5 61934e089]](System.Type myParam)

Answer 1

Unity为Type参数定义提供了特殊处理.有关详细信息,请参阅Krzysztof Kozmic的这篇文章:http://kozmic.pl/2008/12/03/unity-framework-and-the-principle-of-the-least-surprise/