c# 调用c++DLL 结构体参数传值的问题

[wgyathuawei]

c++ DLL 函数原型：int SDK_GetDeviceList(CAMERA_INFO* pDeviceList)；
c++ 结构体：CAMERA_INFO定义：
typedef struct
{
unsigned int uiTotal; //总记录数
CAMERA_INFO_LIST stCameraInf[1]; //结构体数组初始化长度为1，遍历uiTotal来取值,
//pDeviceList->stCameraInfo[index].CameraName
}CAMERA_INFO;

typedef struct
{
string CameraID;
string CameraName;
}CAMERA_INFO_LIST

C# 声明函数：
[DllImport(@"SDK.dll", CallingConvention = CallingConvention.StdCall)]
extern static int SDK_GetDeviceList(ref CAMERA_INFO);

c# 结构体定义
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
struct CAMERA_INFO
{
public uint uiTotal;// 总记录数
[MarshalAs(UnmanagedType.ByValArray,SizeConst = 1000)]
public CAMERA_INFO_LIST[] stCameraInf;
};

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
struct CAMERA_INFO_LIST
{
string CameraID;
string CameraName;
};

c#调用C++Dll：
CAMERA_INFO info = new CAMERA_INFO();
int result = SDK_GetDeviceList(ref info);

这样调用能够取到值， [MarshalAs(UnmanagedType.ByValArray,SizeConst = 1000)]中SizeConst必须赋值，
问题是在调用之前不知道返回CAMERA_INFO_LIST数组长度是多少，使用时只能赋一个很大的数值；想问下有
没有什么方法，SizeConst不赋初始值，根据uiTotal来分配呢

[Trent1985]

用回调试一下！

[soaringbird]

typedef struct { string CameraID; string CameraName; }CAMERA_INFO_LIST C++代码里这个真的是string吗？

[soaringbird]

把你C++原型和调用代码都贴出来

[wgyathuawei]

引用 2 楼 soaringbird 的回复:

typedef struct { string CameraID; string CameraName; }CAMERA_INFO_LIST C++代码里这个真的是string吗？

-----谢谢关注 不是，是char CameraID[100],CameraName[100];我为了简单写成这样了，这个不会影响我问题问题

[wgyathuawei]

引用 3 楼 soaringbird 的回复:

把你C++原型和调用代码都贴出来

C++原型 c++ DLL 函数原型：int SDK_GetDeviceList(CAMERA_INFO* pDeviceList)； c++ 结构体：CAMERA_INFO定义： typedef struct { unsigned int uiTotal; //总记录数 CAMERA_INFO_LIST stCameraInf[1]; //结构体数组初始化长度为1，遍历uiTotal来取值, //pDeviceList->stCameraInfo[index].CameraName }CAMERA_INFO; typedef struct { string CameraID; string CameraName; }CAMERA_INFO_LIST

[soaringbird]

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
        unsafe struct CAMERA_INFO
        {
            public uint uiTotal;// 总记录数
            public CAMERA_INFO_LIST* stCameraInf;
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
        unsafe struct CAMERA_INFO_LIST
        {
            public fixed byte _CameraID[100];
            public string CameraID
            {
                get
                {
                    fixed (byte* p = _CameraID)
                    {
                        return Marshal.PtrToStringAuto(new IntPtr(p));
                    }
                }
            }
            public fixed byte _CameraName[100];
            //get
        };

        [DllImport(@"SDK.dll", CallingConvention = CallingConvention.StdCall)]
        extern static int SDK_GetDeviceList(CAMERA_INFO* pcInfo);