从 C# 调用 C++ dll 函数:结构体、字符串和 wchar_t 数组
-
22-08-2019 - |
题
这是我需要解决的一个简单问题,但它让我感觉我的头发变白了,因为我所有的尝试都返回了同样的错误:
“尝试读取或写入受保护的内存。这通常表明其他内存已损坏。”
我有一个用 C++ 编写的示例应用程序,它调用 dll。这是相关代码:
//function I need to call
bool convertHKID_Name(char *code,RECO_DATA *o_data); //hkid
//struct definition
struct RECO_DATA{
wchar_t FirstName[200];
wchar_t Surname[200];
};
//how it is used in C++ code
CString code;
RECO_DATA data;
GetDlgItemText(IDC_CODE,code);
char _code[200];
WideCharToMultiByte(CP_UTF8, 0, code, -1, (char *)_code, 200, NULL, NULL);
ocr->convertHKID_Name(_code,&data)
现在,当我调试 C++ 代码时,它会执行正确的操作 - 将一些 Unicode 数据写入数据结构中。
这是我在 C# 中尝试做同样的事情
//my C# wrapper class
public class cnOCRsdk
{
[StructLayout(LayoutKind.Sequential, Size=400, CharSet=CharSet.Unicode), Serializable]
public struct RECO_DATA
{
[MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 200)]
public string FirstName;
[MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 200)]
public string Surname;
};
[DllImport(@"cnOCRsdk.dll", CharSet=CharSet.Auto, EntryPoint = "?convertHKID_Name@CcnOCRsdk@@QAE_NPADPAURECO_DATA@@@Z")]
public static extern bool convertHKID_Name(ref string num, ref RECO_DATA o_data);
[DllImport("Kernel32.dll")]
public static extern int WideCharToMultiByte(uint CodePage, uint dwFlags,
[In, MarshalAs(UnmanagedType.LPWStr)]string lpWideCharStr,
int cchWideChar,
[Out, MarshalAs(UnmanagedType.LPStr)]StringBuilder lpMultiByteStr,
int cbMultiByte,
IntPtr lpDefaultChar, // Defined as IntPtr because in most cases is better to pass
IntPtr lpUsedDefaultChar // NULL
);
}
//my attempt to call the function from the dll
cnOCRsdk.RECO_DATA recoData = new cnOCRsdk.RECO_DATA();
string num = "262125355174";
StringBuilder sb = new StringBuilder(200, 200);
cnOCRsdk.WideCharToMultiByte(65001, 0, num, -1, sb, 200, IntPtr.Zero, IntPtr.Zero);
string sbTostring = sb.ToString();
//the next line generates the 'Attempted to read or write protected memory' error
bool res = cnOCRsdk.convertHKID_Name(ref sbTostring, out recoData);
我的猜测是,我没有正确封送 RECO_DATA 结构,因为 ConvertHKID_Name 函数写入的是这个结构。但我该如何解决呢?
解决方案
我相信它应该有效,如果你
- 更改声明
convertHKID_Name
到CharSet.Ansi
- 从字符串参数中删除“ ref”
- 通过
string num
直接到convertHKID_Name
而不是打电话WideCharToMultiByte
其他提示
不隶属于 StackOverflow