如何將C＃託管的結構傳遞給C++非託管DLL並在結果中獲取結構體？

Question

我不太瞭解C++，所以我添加了所有的dll代碼。

C++ ** ** Calculator.h

#ifndef CALCULATOR_H 
#define CALCULATOR_H 

#include "global.h" 

struct CALCULATORSHARED_EXPORT Input { 
    double a; 
    double b; 
}; 

struct CALCULATORSHARED_EXPORT Result { 
    double sum; 
    double diff; 
    double prod; 
    double div; 
}; 

global.h

#ifndef CALCULATOR_GLOBAL_H 
#define CALCULATOR_GLOBAL_H 

#if defined(CALCULATOR_EXPORTS) 
# define CALCULATORSHARED_EXPORT __declspec(dllexport) 
#else 
# define CALCULATORSHARED_EXPORT __declspec(dllimport) 
#endif 

#endif // CALCULATOR_GLOBAL_H 

calculator.h

#include "calculator.h" 

Result calculate(const Input& input) { 
    Result result; 

    result.sum = input.a + input.b; 
    result.diff = input.a - input.b; 
    result.prod = input.a * input.b; 
    result.div = input.a/input.b; 

    return result; 
} 

C＃

[DllImport("Calculator.dll", CallingConvention = CallingConvention.Cdecl)] 
     public static extern Result calculate(Input input); 


     [StructLayout(LayoutKind.Sequential)] 

     public struct Input 
     { 
      public double a; 
      public double b; 
     }; 

     [StructLayout(LayoutKind.Sequential)] 

     public struct Result 
     {    
      public double sum; 
      public double diff; 
      public double prod; 
      public double div; 
     }; 

     private void button1_Click(object sender, EventArgs e) 
     { 
      Input input; 
      Result result; 
      input.a = 5; 
      input.b = 6; 
      result = calculate(input);  
     } 

我越來越Unable to find an entry point named 'calculate' in DLL 'Calculator.dll'.

Answer 1

你要做的：

extern "C" 
{ 
    CALCULATORSHARED_EXPORT Result calculate(const Input& input) 
    { 
    } 
} 

你並不需要標記CALCULATORSHARED_EXPORT兩個結構（Input和Result）。

該extern "C"否則函數的名稱將被損壞，否則CALCULATORSHARED_EXPORT函數將不會被導出。

和C＃簽名必須是：

public static extern Result calculate(ref Input input); 

因爲在C++中，它是一個Input&。

那麼很顯然

result = calculate(ref input);