Question

c#调c++dll，ref结构体，报错“尝试读取或写入受保护的内存。这通常指示其他内存已损坏”

c++中：
typedef struct tagINVOICEDATA {
char szFpCryptograph[116];
char szFpEnVersion[8];
char szFpCode[16];
char szFpSeriaoNo[16];
char szFpDate[8];
char szFpBuyerTaxNo[22];
char szFpSellerTaxNo[22];
char szFpSum[32];
char szFpTaxRate[16];
char szFpTax[32];
char szFpTotal[32];
char szFpTaxDiskNo[16];
char szFpImage[256];
char szBarCodePic[252];
char *BarCodeData;
int nBarCode;
} INVOICEDATA, *PINVOICEDATA;

typedef int (WINAPI *lpFpGetNewPage)(PINVOICEDATA lpFpBuffer);
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c#中：
[StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
public struct tagINVOICEDATA//string
{
#region

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 116)]
public string szFpCryptograph;
/// <summary>
/// 加密版本号
/// </summary>
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)]
public string szFpEnVersion;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)]
public string szFpCode;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)]
public string szFpSeriaoNo;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)]
public string szFpDate;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 22)]
public string szFpBuyerTaxNo;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 22)]
public string szFpSellerTaxNo;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string szFpSum;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)]
public string szFpTaxRate;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string szFpTax;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string szFpTotal;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)]
public string szFpTaxDiskNo;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string szFpImage;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 252)]
public string szBarCodePic;
[MarshalAs(UnmanagedType.LPStr)]
public string BarCodeData;
public int nBarCode;

#endregion

}

[DllImport("Scanreco.dll", CharSet = CharSet.Ansi, ExactSpelling = true, EntryPoint = "FpGetNewPage", CallingConvention = CallingConvention.StdCall)]
public static extern int FpGetNewPage(ref tagINVOICEDATA FpBuffer);

tagINVOICEDATA invoicedata = new tagINVOICEDATA();

int rst = ScanrecoC.FpGetNewPage(ref invoicedata);这个就报内存错呢？

Answer 1

关于结构体传参，给你个链接，看看第四个。

网页链接

另外，涉及回调有点麻烦。要用c++的回调，需要在c#里声明一个对应的委托。

内存方面，c#的new和c++new出来的内存好像不一样。容易出错。

结构体里倒数第二个，关于char*，c#里获取这个char*要用stringbuilder拿到。