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