问题描述

我正在尝试为通用接口方法创建一个 开放实例委托，但我不断收到 NotSupportedException.这是不会运行的简化代码:

I'm trying to create an open instance delegate for a generic interface method, but I keep receiving a NotSupportedException. Here is the simplified code that won't run:

interface IFoo
{
    void Bar<T>(T j);
}
class Foo : IFoo
{
    public void Bar<T>(T j)
    {
    }
}
static void Main(string[] args)
{
    var bar = typeof(IFoo).GetMethod("Bar").MakeGenericMethod(typeof(int));
    var x = Delegate.CreateDelegate(typeof(Action<IFoo, int>), null, bar);
}

最后一行抛出 NotSupportedException，不支持指定的方法".相比之下，非泛型开放实例委托运行良好:

The last line throws NotSupportedException, "Specified method is not supported". By comparison, a non-generic open instance delegate runs fine:

interface IFoo
{
    void Bar(int j);
}
class Foo : IFoo
{
    public void Bar(int j)
    {
    }
}
static void Main(string[] args)
{
    var bar = typeof(IFoo).GetMethod("Bar");
    var x = Delegate.CreateDelegate(typeof(Action<IFoo, int>), null, bar);
}

封闭的通用委托也可以:

And a closed generic delegate also works:

interface IFoo
{
    void Bar<T>(T j);
}
class Foo : IFoo
{
    public void Bar<T>(T j)
    {
    }
}
static void Main(string[] args)
{
    var bar = typeof(IFoo).GetMethod("Bar").MakeGenericMethod(typeof(int));
    var x = Delegate.CreateDelegate(typeof(Action<int>), new Foo(), bar);
}

因此，封闭式泛型委托和开放式实例委托的秘诀是分开工作，但在组合时则不然.它开始看起来像是运行时错误或故意遗漏.有人对此有任何见解吗?

So the recipe for closed generic delegates and open instance delegates work separately, but not when combined. It's starting to look like either a runtime bug, or intentional omission. Anyone have any insight here?

推荐答案

微软已经回答，CLR 无法做到这一点是一个已知问题，但在当前版本的 .网.正如我在那儿解释的那样，为什么这仍然是不可能的.出于某种原因，开放委托不能重用 CLR 中其他地方使用的调度逻辑，这对我来说似乎很奇怪.

Microsoft has answered that it's a known problem that the CLR can't do this, but it can't be solved in the current version of .NET. It's still not at all clear why this isn't possible as I explain there. Open delegates must not reuse the dispatching logic used everywhere else in the CLR for some reason, which just seems bizarre to me.

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