我被要求将网络摄像头 ZoneTrigger 集成到我的项目中。站点中提供的 SDK 也是 C++ 示例。我已经能够让一些功能正常工作。我陷入困境的地方是一个函数,其中 char* 是传递的参数。我做了很多挖掘,并且知道必须使用 MarshalAs...
我想要导入的函数 C++代码
//header file
struct ZT_TRIG_STRUCT
{
int aSize; //STRUCT size
int CameraIndex;
int SpotIndex;
int SpotType;
char SpotName[32];
DWORD Dummy[16];
};
typedef int (WINAPI *f_ZT_EnumerateHotSpots)(int SpotIndex, char *Name, int *SpotType);
/*
You application can call this functions to retrieve information about spots by iterating the SpotIndex param.
Name is a pointer to a 32 byte buffer supplied by your application.
SpotType is a pointer to an 32 bit integer in your application.
Return value:
0 = Success, the Name and SpotType have been initialized
1 = Error, we have lost communication with Zone Trigger
2 = Enumaration is over, all spots have been enumerated. Your application should increment SpotIndex until this function returns 2.
*/
//code
//Enumerate current spots in Zone Trigger
int i=0;
char SpotName[32];
int SpotType;
check = ZT_EnumerateHotSpots(i, SpotName, &SpotType);
while (check == 0)
{
float sensitivity = ZT_GetSensitivity(i);
printf("Zone Trigger spot: %s Sensitivity: %0.1f%%\r\n", SpotName, sensitivity*100);
check = ZT_EnumerateHotSpots(++i, SpotName, &SpotType);
}
所以当转换为c#时
[DllImport("ZTcom.dll")]
private static extern int ZT_EnumerateHotSpots(int i, [MarshalAs(UnmanagedType.LPWStr)]ref string SpotName, ref int SpotType);
public unsafe struct ZT_TRIG_STRUCT
{
public int aSize; //STRUCT size
public int CameraIndex;
public int SpotIndex;
public int SpotType;
public string SpotName ;
//[MarshalAs(UnmanagedType.LPStr, SizeConst = 256)] string SpotName;
// public IntPtr SpotName;
}
//In code
int i = 0;
string SpotName;
int SpotType;
check = ZT_EnumerateHotSpots(i, ref SpotName, ref SpotType);
上面的行给出:
Exception of type 'System.ExecutionEngineException' was thrown.
错误。
我知道问题出在 SpotName 中,它是一个字节 [32],如果我不使用 marshalAs,而是只使用 char 它可以工作 n 给出第一个字符.. 工作正常的代码 n 给出第一个字符如下
public unsafe struct ZT_TRIG_STRUCT
{
public int aSize; //STRUCT size
public int CameraIndex;
public int SpotIndex;
public int SpotType;
public char SpotName ;
}
[DllImport("ZTcom.dll")]
private static extern int ZT_EnumerateHotSpots(int i, ref char SpotName, ref int SpotType);
public char SpotName;
int i = 0;
check = ZT_EnumerateHotSpots(i, ref SpotName, ref SpotType);
while (check == 0)
{
float sensitivity = ZT_GetSensitivity(i);
textBox1.Text = textBox1.Text + "\r\n" +"Zone Trigger spot: " + SpotName + " Sensitivity: " + (sensitivity * 100).ToString();
check = ZT_EnumerateHotSpots(++i, ref SpotName, ref SpotType);
}
但是如果我输入 char[] 它会给出
Method's type signature is not Interop compatible. ERROR
我已经没有选择了......我哪里出了问题?我应该使用 MarshalAs 还是 char[]??? 请帮忙..... 提前致谢....
最佳答案
我看不到您在哪里使用 ZT_TRIG_STRUCT
,但应该这样声明:
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi)]
public struct ZT_TRIG_STRUCT
{
public int aSize;
public int CameraIndex;
public int SpotIndex;
public int SpotType;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)]
public string SpotName;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=16)]
public uint[] Dummy;
}
您遇到的另一个问题是在 ZT_EnumerateHotSpots
的声明中。应该是:
[DllImport("ZTcom.dll", CharSet=CharSet.Ansi)]
private static extern int ZT_EnumerateHotSpots(
int SpotIndex,
StringBuilder SpotName,
out int SpotType
);
正如我所读,SpotName
实际上是一个输出参数,即您提供一个缓冲区,ZT_EnumerateHotSpots
写入它。
然后你可以这样调用它
int SpotIndex = 0;
StringBuilder SpotName = new StringBuilder(32);
int SpotType;
int result = ZT_EnumerateHotSpots(SpotIndex, SpotName, out SpotType);
关于c# - C# 中的 C++ 非托管 DLL,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7318613/