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Hi,

I have exported a C++ method to C# and using list of structure in both the places. But when i am inserting the list from C++ to C# method it throws me write access violation. Below is the code reference.

What I have tried:

C++ Code:
.h File:
struct DBAData
{
long id;
char name;

--
--
}

.Cpp file:
extern "C" __declspec(dllexport) void __cdecl TableData(std::list<DBAData> ReturnData)
	{
		
		std::list<DBAData> eventDB;
		
		GetTableData(4, eventDB);
		
		std::copy(eventDB.begin(), eventDB.end(),
			std::back_insert_iterator<std::list<DBAData> >(ReturnData));// Fails here
}



C# Code:

cs file:
public struct Data
    {
        public long id;
        public char name;
--
--
--
    }

    public class Test
    {
        [DllImport("Data.DLL")]
         public static extern void TableData(IList<Data> return)
    }

void function()
{
 IList<Data> retValue = new List<Data>();
 Test.TableData(retValue);
}



First thing can we map list<structure> from C++ to Ilist<structure> in C# , as i need to export list of data from C++ to C#. Or is there any other best way to do it.

Thanks in Advance.
Posted
Updated 6-Apr-21 5:45am

As far as I'm aware you can't marshall something like a list, because these sorts of objects are implemented differently across C# and C++. You need to instead look at returning or consuming something much simpler, like an array instead. I'd recommend having the C++ method require an array of Data and also provide an int indicating the length of the array. You could then convert it into a list within the C++ method to perform whatever operations you need.

c++ - How to return a list in C# using P/Invoke? - Stack Overflow[^]
   
I am willing to bet it's because you are trying to store a name in a single char. Of course, I could be wrong.

That's just one issue though. Solution 1 outlined the bigger problem you have and possible work-around. Once you have done that then you will have to deal with the name issue.
   

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