Question

似乎我在.NET-2.0 / unity的.NET-2.0中发现了一个奇怪的错误。

public class Test
{
    public interface ICovariant<out T>
    {
        T GetT();
    }

    public class Covariant<T>: ICovariant<T>
    {
        public T GetT()
        {
            throw new NotImplementedException();
        }
    }

    public interface IFoo
    {
    }

    public class Bar : IFoo
    {
    }

    public class CovariantHolder
    {
        public CovariantHolder(ICovariant<IFoo> covariant)
        {
        }
    }

    public class CovariantBar: Covariant<Bar>
    {
    }

    public static void Main(string[] args)
    {
        ICovariant<IFoo> foo = new Covariant<IFoo>();
        ICovariant<IFoo> foobar = new Covariant<Bar>();
        ICovariant<IFoo> bar = new CovariantBar();
        CovariantBar barbar = new CovariantBar();

        new CovariantHolder(foo);     // works
        new CovariantHolder(foobar);  // works
        new CovariantHolder(bar);     // works
        new CovariantHolder(barbar);  // works

        Console.WriteLine(typeof(ICovariant<IFoo>).IsAssignableFrom(typeof(Covariant<IFoo>))); // true;
        Console.WriteLine(typeof(ICovariant<IFoo>).IsAssignableFrom(typeof(Covariant<Bar>)));  // true;
        Console.WriteLine(typeof(ICovariant<IFoo>).IsAssignableFrom(typeof(CovariantBar)));    // false! what?;

        typeof(CovariantHolder).GetConstructors()[0].Invoke(new object[] {foo});      //works
        typeof(CovariantHolder).GetConstructors()[0].Invoke(new object[] {foobar});   //fails! WHAAT?
        typeof(CovariantHolder).GetConstructors()[0].Invoke(new object[] {bar});      //fails!
        typeof(CovariantHolder).GetConstructors()[0].Invoke(new object[] {barbar});   //fails!
    }
}

AFAIK，unity使用mono 2.0.50727.1433

周围有什么办法吗？我可以使用协变参数通过反射来设置对象吗？

UPD ：错误代码： InvalidCastException: Value is not a convertible object: Test+Covariant``1[GameInstaller+Bar] to Test+ICovariant``1[[Test+IFoo, Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null]]

使用反射的协变对象实例化

0 个答案: