C# 调用C++DLL传递指向指针的指针参数的方法

C++结构体定义：

struct DeviceInfo
{    
    char szDeviceName[DEVICE_NAME_LEN];
    char szMACAddress[MAC_ADDRESS_LEN];        
    char szDeviceIP[DEVICE_IP_LEN];
};

C#结构体的定义：

    [StructLayout(LayoutKind.Sequential)]
   public struct DeviceInfo
    {
          [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
        public string szDeviceName;

         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 13)]
          public string szMACAddress;

         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 17)]
         public string szDeviceIP; 


    }

情况1：C++的dll负责分配内存

C++导出函数的声明

#define DLL_API  extern "C"  __declspec(dllexport)
DLL_API int findAllDevices(DeviceInfo** ppDeviceInfoList,int * pCount);

C#导入函数的声明

[DllImport("IPAlter_d.dll")]
        public extern static int findAllDevices(out IntPtr pDeviceInfo, ref int pCount);

C#的调用方法：

 IntPtr pBuff = new IntPtr();//直接new一个参数即可



            if (IPAlter.findAllDevices(out pBuff, ref cout) != 1)
            {
                System.Console.WriteLine("搜索失败！");
                System.Console.ReadLine();
                return;
            }

          
            for (int i = 0; i < cout; i++)
            {

                IntPtr pPonitor = new IntPtr(pBuff.ToInt64() + Marshal.SizeOf(typeof(DeviceInfo)) * i);
              

              System.Console.WriteLine(((DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo))).szDeviceName);
                System.Console.WriteLine(((DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo))).szDeviceIP);
                System.Console.WriteLine(((DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo))).szMACAddress);
            }

情况2：C#负责分配内存

C++导出函数的声明:

DLL_API int findAllDevice(DeviceInfo* ppDeviceInfoList,int * pCount);

 C#导入函数的声明:

 [DllImport("IPAlter_d.dll")]
        public extern static int findAllDevice(IntPtr pDeviceInfo, ref int pCount);

 C#的调用方法：

            DeviceInfo[] DeviceInfoList = new DeviceInfo[50];
            int size = Marshal.SizeOf(typeof(DeviceInfo)) * 50;
            byte[] bytes = new byte[size];
            IntPtr pBuff = Marshal.AllocHGlobal(size);



            if (IPAlter.findAllDevice(pBuff, ref cout) != 1)
            {
                System.Console.WriteLine("搜索失败！");
                System.Console.ReadLine();
                return;
            }


            for (int i = 0; i < cout; i++)
            {

                IntPtr pPonitor = new IntPtr(pBuff.ToInt64() + Marshal.SizeOf(typeof(DeviceInfo)) * i);
                DeviceInfoList[i] = (DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo));

                System.Console.WriteLine(DeviceInfoList[i].szDeviceName);
                System.Console.WriteLine(DeviceInfoList[i].szDeviceIP);
                System.Console.WriteLine(DeviceInfoList[i].szMACAddress);
            }
            Marshal.FreeHGlobal(pBuff);

可以参考：

http://www.cnblogs.com/cxwx/archive/2010/12/29/1921140.html

http://hi.baidu.com/fanr520/item/e761f9ca0766d462f6c95d55

http://blog.csdn.net/wangweitingaabbcc/article/details/7663949