Question 266143 in Visual Studio Code Question posted in
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Visual Studio Code – How to pass the vector data from c# to C++ and get the vector data from C++ to c#?

I am new to C# and visual studio. I have wrote one function in C++.
I need to encapsulate C++ functions into dynamic link libraries(DLL),and then using C# to call C++ to operate vector data n parameters.

Here is my main function.

#include "pch.h"
#include <time.h>
#include <vector>
#include<iostream>
Void cal_lenth(double length,std::vector<int>length_par, std::vector<int> &length_final, std::vector<std::vector<int>> &bb_vec){
   //int length=100;
   //std::vector<int> length_par = {5,6,7,8,9};
   for (int i = 0; i < length_par.size(); i++) {
       length_final[i]=length_par[i];
       std::cout<<length_final[i];
       }
      std::cout<<std::endl;
   }
std::vector<std::vector<int>> bb;
   for (int i = 0; i < 5; i++) {
    bb_vec.push_back(length_par);
   }
   std::cout<<"endend"<<std::endl;
}

And here is my .h file:

#define IMPORT_DLL extern "C" _declspec(dllimport)
#ifndef PCH_H
#define PCH_H
#include <cstdlib>
#include <string>
#include <numeric>
#include <time.h>
using namespace std;
IMPORT_DLL void cal_lenth(double length,std::vector<int>length_par, std::vector<int> &length_final, std::vector<std::vector<int>> &bb_vec);
#endif //PCH_H

Here is my calling function "ConsoleApp1" for DLL files:
Now I compiled the code to DLL using newest Cmake and VS2022.I want to input the parameters(double length,std::vectorlength_par), and get the result in C#( std::vector &length_final, std::vectorstd::vector<int> &bb).

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;
using static ConsoleApp1.Program;

namespace ConsoleApp1
{
    internal class Program
    {
        private double length;
        public class Vector
        {
            //private double length;
            private double[] length_par;
            public int Length_len => length_par.Length;
        }
        [StructLayout(LayoutKind.Sequential)]
        public struct Length_par
        {
            public double length;
            //public Vector length_par = new double Vector();
            public double a;
            public double b;
            public double c;
        }
        [DllImport("pch.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern void cal_lenth(ref double length, ref Vector length_par,ref Vector &length_final,ref Vector &bb_vec);
        Length_par length_par = new Length_par();
        length_par.Add (1); //wrong
         
            
        //int result = cal_lenth(length_par);
        static void Main()
        {
            double length  = 100;
            //Vector length_par = new Vector();
            //length_par.a = 1;
            Vector num_par = new Vector();
            cal_lenth(ref length, ref length_par,out length_final,out Vector &bb_vec);

        }

    }
}

I tried to write a correct call file that was feasible when running a function without input and output parameters, but when I added parameters to the function, I failed. I have tried many ways to write call function,so my code is a bit confusing, and even my ideas are completely incorrect,I sincerely hope to receive your suggestions and corrections!Thank u!

Tags:

2

Answers


  1. 0

    It appears that you want to call a C++ function from a DLL in C# with certain input and output parameters. To do this, you need to make sure your C++ code is properly wrapped in a DLL and the C# code is correctly set up to call it.

    C++ Code: Your C++ code appears to be almost correct, but there are a few issues. In your function declaration and definition, the data types of length_par, length_final, and bb_vec don’t match in C++ and C#. You should use arrays for length_par and length_final in C++, as follows:

    IMPORT_DLL void cal_lenth(double length, int* length_par, int length_par_size, int* length_final, int length_final_size, int** bb_vec, int bb_vec_size);

    C# Code: Your C# code also needs some adjustments:

    Create appropriate managed structures that match the C++ parameters.
    Use MarshalAs attributes to ensure data is marshaled correctly.
    Make sure to use IntPtr for arrays to correctly marshal them to C++.
    Here’s an example of how your C# code should look:

    using System;
using System.Runtime.InteropServices;

namespace ConsoleApp1
{
    internal class Program
    {
        [DllImport("pch.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern void cal_lenth(
            double length,
            [In, MarshalAs(UnmanagedType.LPArray)] int[] length_par,
            int length_par_size,
            [In, Out, MarshalAs(UnmanagedType.LPArray)] int[] length_final,
            int length_final_size,
            [In, Out, MarshalAs(UnmanagedType.LPArray)] IntPtr[] bb_vec,
            int bb_vec_size
        );

        static void Main()
        {
            double length = 100;
            int[] length_par = new int[] { 5, 6, 7, 8, 9 };
            int[] length_final = new int[length_par.Length];
            IntPtr[] bb_vec = new IntPtr[5]; // Assuming you want an array of arrays

            cal_lenth(length, length_par, length_par.Length, length_final, length_final.Length, bb_vec, bb_vec.Length);

            // Now, you can work with 'length_final' and 'bb_vec' in C#
            // Don't forget to clean up memory if necessary.
        }
    }
}

    Memory Management: In C#, you should allocate memory for the bb_vec elements before calling cal_lenth and then free the memory after you’re done with the data to prevent memory leaks.
    This code should help you call your C++ function from C#. Please ensure that you’ve properly compiled your C++ code into a DLL and that the DLL is accessible from your C# project.

    Hope this is the solution you were looking for!

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  2. 0

    As the comments said, avoid using standard library types across the .net boundary.
    Considering dynamic arrays are required and your example does not have specific C++ third party library, it will be more convenient to use C# code. Such as :

       static void CalLength(double length, List<int> lengthPar, List<int> lengthFinal, List<List<int>> bbVec)
    {
        for (int i = 0; i < lengthPar.Count; i++)
        {
            lengthFinal[i] = lengthPar[i];
            Console.WriteLine(lengthFinal[i]);
        }
        Console.WriteLine();

        for (int i = 0; i < 5; i++)
        {
            bbVec.Add(new List<int>(lengthPar));
        }

        Console.WriteLine("endend");
    }
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