调用C++函数,参数是结构体,结构体里再带指针，取不到返回值

--------------------编程问答-------------------- --------------------编程问答-------------------- 我即使预先分配内存到结构体变量中,结果还是一样.



        private IntPtr InitQueue(int nSize)

        {

            IntPtr pt = IntPtr.Zero;

            int nStructSize = Marshal.SizeOf(typeof(HoloQueueItem));

            if (nSize > 0)

            {

                HoloQueueItem[] queue = new HoloQueueItem[nSize];

                IntPtr[] ptArray = new IntPtr[1];

                ptArray[0] = Marshal.AllocHGlobal(nStructSize * nSize);

                pt = Marshal.AllocHGlobal(nStructSize);

                Marshal.Copy(ptArray, 0, pt, 1);

            }

            return pt;

        }



// 函数调用

            HoloPosition pHolo = new HoloPosition();

            pHolo.pHeadOfAskQueue = InitQueue(2000);

            pHolo.pHeadOfBidQueue = InitQueue(2000);

            pHolo.marketData = new HoloMarketData();



            IntPtr pData = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(HoloPosition)));



            Marshal.StructureToPtr(pHolo, pData, true);



            TDF_GetHoloPosition(strMarket, strCode, ref pData);

--------------------编程问答--------------------

[DllImport("")]

extern static int GetPosition([MarshalAs(UnmanagedType.LPStr)]string lpMarket, [MarshalAs(UnmanagedType.LPStr)]string lpCode, HoloPosition* pReqHoloData);



[StructLayout(LayoutKind.Sequential)]

unsafe struct HoloPosition

{

    public fixed byte szMarKet[8];

    public fixed byte szCode[16];



    public int nSizeOfAskQueue;

    public HoloQueueItem* pHeadOfAskQueue;



    public int nCountOfBidQueue;

    public HoloQueueItem* pHeadOfBidQueue;



    HoloMarketData marketData;//这个类型未知

}



[StructLayout(LayoutKind.Sequential)]

struct HoloQueueItem

{

    public int nTime;

    public int nPrice;

    public int nVolume;

    public int nNumOrder;

}



//调用

HoloPosition data;

GetPosition(strMarket, strCode, &data);

--------------------编程问答--------------------





    public struct HoloMarketData

    {

        public int nTime;                       

        public int nPreClose;	                

        public int nOpen;		                

        public int nHigh;		                

        public int nLow;		                

        public int nMatch;		                



        public int nNumTrades;	                

        public Int64 iVolume;		            

        public Int64 iTurnover;		            



        public Int64 iTotalBidVol;	            

        public Int64 iTotalAskVol;	            

    }

--------------------编程问答-------------------- HoloMarketData 最后4个成员在 C/C++ 结构中如果是 long ，就按如下结构

[StructLayout(LayoutKind.Sequential)]

unsafe struct HoloMarketData

{

    public int nTime;

    public int nPreClose;

    public int nOpen;

    public int nHigh;

    public int nLow;

    public int nMatch;



    public int nNumTrades;

    public void* iVolume;

    public void* iTurnover;



    public void* iTotalBidVol;

    public void* iTotalAskVol;

}

和3楼的代码组合使用

补充：.NET技术 ,  C#