与REF /指针参数C＃反射调用方法 [英] C# Reflection Call Method with ref/Pointer Parameter

问题描述

我想与反思的每个类的方法来调用，但我不能调用方法与指针作为参考。通常我只可以传递null每个指针我发现，一切都将被罚款。问题是，当函数改掉访问我传递指针。指针将是内存地址0的参考，这是很明显对我的计划瞬间崩溃。
所以我需要一个指针传递给一个有效的内存ADRESS，但我不知道我怎么可以创建在运行时的指针

I want to call with reflection each Method of an Class but I cant call Methods with an pointer as Reference. Normally I just could pass null for each pointer I find and everything would be fine. The Problem is when the function trys to access my passed pointer. The pointer would be an reference to the memory address 0 and that is obviously an instant crash for my Program. So I need to pass an pointer to an valid memory adress, but I dont know how I can create an pointer during runtime

一个压缩我的代码版本

class Program
{
    static void Main(string[] args)
    {
        var obj = new TestClass();
        var pointerMethod = obj.GetType().GetMethod("Test");
        var referenceMethod = obj.GetType().GetMethod("Test2");

        var pointerParameter = pointerMethod.GetParameters()[0];
        var referenceParameter = referenceMethod.GetParameters()[0];

        //Get the instance of the class that is referred by the pointer/reference
        var pointerInstance = Activator.CreateInstance(pointerParameter.ParameterType.GetElementType());
        var referenceInstance = Activator.CreateInstance(referenceParameter.ParameterType.GetElementType());

        //Call the method and "cast" the char instance into an pointer
        pointerMethod.Invoke(obj, new[] {pointerInstance.GetType().MakePointerType()});
        referenceMethod.Invoke(obj, new[] { referenceInstance.GetType().MakeByRefType() });
     }
}

和TestClass的：

And TestClass:

public class TestClass
{
        unsafe public void Test(char* pointer)
        {

        }

        public void Test2(ref int reference)
        {

        }
}

我总是得到异常System.RuntimeType不能转换为类型'System.Char *'
奇怪的是，pointerInstance.GetType （）.MakePointerType（）返回一个char *，正是我要传递给函数...

I've always get the Exception "System.RuntimeType" cannot be converted to type 'System.Char*' The weird thing is that pointerInstance.GetType().MakePointerType() returns a char*, exactly that what I have to pass into the function...

推荐答案

第一，让我们这个分成指针VS REF - 他们正在处理略有不同。

First, let's separate this into pointer vs ref - they're handled slightly differently.

目前还不清楚是什么指针值您的有望的方法来领取 - 尤其当你传递给调用是一个类型，而不是类型的实例的价值 - 但你应该使用 Pointer.Box ：

It's not clear what pointer value you expected the method to receive - particularly as the value you passed to Invoke was a type, not an instance of the type - but you should use Pointer.Box:

using System.Reflection;

class TestPointer
{    
    unsafe static void Main()
    {
        char c = 'x';
        char* p = &c;
        object boxedPointer = Pointer.Box(p, typeof(char*));

        var method = typeof(TestPointer).GetMethod("Foo");
        method.Invoke(null, new[] { boxedPointer });
        Console.WriteLine("After call, c = {0}", c);
    }

    public static unsafe void Foo(char *pointer)
    {
        Console.WriteLine("Received: {0}", *pointer);
        *pointer = 'y';
    }
}

输出：

Output:

Received: x
After call, c = y

有关 REF 参数，它是稍微简单 - 你只允许正常的拳击，和参数数组改变了：

For ref parameters, it's slightly simpler - you just allow for normal boxing, and the argument array is changed:

using System.Reflection;

class TestRef
{    
    unsafe static void Main()
    {
        var method = typeof(TestRef).GetMethod("Foo");
        var args = new object[] { 10 };
        method.Invoke(null, args);
        Console.WriteLine("After call, args[0] = {0}", args[0]);
    }

    public static unsafe void Foo(ref int x)
    {
        Console.WriteLine("Received: {0}", x);
        x = 20;
    }
}

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