c函数将结构返回给c＃ [英] c function that return a struct to c#

问题描述

您好，

我有一个返回结构的交流函数，我已经构建了一个.dll，我想从c＃中调用它，如下所示：

i have a c function that return a structure, i have build a .dll and i want to call it from c# like this:

typedef struct predtionresult {

    float prediction[5];
    char *name[5];
}PREDICTIONRESULT;


PREDICTIONRESULT predict()
{
    PREDICTIONRESULT predres ;

    for(i = 0; i < 5; ++i){

        predres.name[i]= names[i]; //names[i] are not empty 
        predres.prediction[i] = predictions[i] // prediction are not empty there is 

//代码的某些部分，我不能分享
}

返回预测;
}

i已经声明了这样的c＃结构：


[StructLayout（LayoutKind.Sequential，CharSet = CharSet.Ansi，Pack = 1） ]
public struct PREDICTIONRESULT {

[MarshalAs（UnmanagedType.ByValArray，SizeConst = 5）]
public float [] prediction;

[MarshalAs（UnmanagedType.ByValTStr，SizeConst = 5）]
public string [] name;
};

//some part of code that i can't share } return predres; } i have declared the c# structure like this: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)] public struct PREDICTIONRESULT{ [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] public float[] prediction; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 5)] public string[] name; };

并调用这样的函数：

PREDICTIONRESULT prediction;

prediction = predict();

问题是预测数组和名称数组是空的，我没有得到返回的值c函数，所以我认为我的c＃结构有一个我没有得到的问题。

The problem is the prediction array and the name array are empty, i didn't get the returned value from the c function, so i think that my c# structure have a problem that i didn't get.

谢谢 

Lafi

推荐答案

嗨读lafi，

Hi Read lafi,

感谢您在此发帖。

我想根据您的C ++代码制作它。但我不擅长C ++。您的C ++代码中存在一些编译器错误。因此，我举了一个简单的例子供你参考。

I want to make it according to your C++ code. But I am not good at C++. There are some complier errors in your C++ code. Hence I make a simple example for your reference.

My C ++ dll

My C++ dll

// MyDll.cpp : Defines the exported functions for the DLL application.
//

#include "stdafx.h"

#define EXPORT_DLL extern "C" __declspec(dllexport) 

EXPORT_DLL int Add(int a, int b)
{
	return a + b;
}
struct Bar
{
public:
	int id;
};

EXPORT_DLL void GetBar(Bar& bar)
{
	//Bar b;
	bar.id = 10;
}

我的C＃代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp
{
    [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
    public struct Bar
    {
        /// int
        public int id;
    }
    class CSharp_call_C__
    {
        [DllImport(@"D:\Visual Studio 2017\Projects\ConsoleApp\Debug\MyDll.dll", EntryPoint = "Add", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
        extern static int Add(int a, int b);

        [DllImport(@"D:\Visual Studio 2017\Projects\ConsoleApp\Debug\MyDll.dll", EntryPoint = "GetBar", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Cdecl)]
        extern static void GetBar(ref Bar bar);

        static void Main(string[] args)
        {
            int A = Add(1, 2);
            Console.WriteLine(Add(5, 4));

            Bar bar = new Bar();
            GetBar(ref bar);
            Console.WriteLine("BAR id is " + bar.id);

            Console.ReadKey();
        }
    }
}

希望它会有所帮助。

最诚挚的问候，

Wendy

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