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String values in struct getting truncated after call to dll

I am trying to use PInvoke to send a structure containing strings to a DLL written in Microfocus COBOL using net7.0 (x86) and some strings appear to be get truncated while marshalling. The structure are read from and written to by the DLL. I don't have access to the source.
The struct looks like
using System.Runtime.InteropServices;
namespace DllImport.Test;
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct TransactionHeader
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string Filler1;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string TransactionCode; //4
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string FunctionCode;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 1)]
public string JuryPopSystemId;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string SystemId;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string tchSystemUserId;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string Filler2;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 10)]
public string SystemPassword;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 1)]
public string DbConnectFlag;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 9)]
public string Jid;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string Pin;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string AltReturnCode;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string AltInfoCode;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string Filler3;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string Filler4;
[MarshalAs(UnmanagedType.I4)] public int tchRtnCdNum;
[MarshalAs(UnmanagedType.I4)] public int tchInfCdNum;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 35)]
public string ErrorMsg;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
public string Reserved;
}
The call is
[DllImport("XXXX.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
public static extern void THECALL([In,Out] ref TransactionHeader hdr, [In, Out] ref udtString128 request,
[In, Out] ref udtCommArea commArea);
After the call, the header has the strings truncated by 1 character. For example, I set the SystemId to "DEVL", but the value is "DEV" after the call. I feel as though I am running to a null terminated string problem, but I wanted to check with people more experienced with PInvoke.
Declaring the struct members as UnmanagedType.LPStr makes no difference.
Thanks.

How to marshal wchar[]

I've found plenty of information about how to marshal wchar_t and wchar* on the internet, but right now I am trying to marshal the WINBIO_STRING type, which is defined as wchar[256]. Marshalling it as an array of char[] works, but then every other element in the array is \0, and I would like to avoid this. Is there a more proper way to marshal this data (which is a member of a struct, the WINBIO_UNIT_SCHEMA struct in particular). This is my code:
[StructLayout(LayoutKind.Sequential)]
public struct BiometricUnitSchema
{
public int UnitId;
public BiometricPoolType PoolType;
public BiometricType BiometricFactor;
public BiometricSubtype SensorSubType;
public BiometricCapabilities Capabilities;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
public char[] DeviceInstanceId;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
public char[] Description;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
public char[] Manufacturer;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
public char[] Model;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
public char[] SerialNumber;
public BiometricVersion FirmwareVersion;
}
I also have the problem of the FirmwareVersion field always containing MajorVersion and MinorVersion values of 0, but I am not sure if this result is incorrect or simply misleading.

I fixed this problem by marshaling WINBIO_STRING as a string in C# instead of a char[]. I also had to add a Unicode charset to my structure.
My new structure:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct BiometricUnitSchema
{
public int UnitId;
public BiometricPoolType PoolType;
public BiometricType BiometricFactor;
public BiometricSubtype SensorSubType;
public BiometricCapabilities Capabilities;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string DeviceInstanceId;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string Description;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string Manufacturer;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string Model;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string SerialNumber;
public BiometricVersion FirmwareVersion;
}

Convert the _WTSClient struct from C++ to C#

I have been trying to convert this struct to C# for the last couple of days, but to no avail...
https://msdn.microsoft.com/en-us/library/windows/desktop/bb736369(v=vs.85).aspx
typedef struct _WTSCLIENT {
TCHAR ClientName[CLIENTNAME_LENGTH + 1];
TCHAR Domain[DOMAIN_LENGTH + 1 ];
TCHAR UserName[USERNAME_LENGTH + 1];
TCHAR WorkDirectory[MAX_PATH + 1];
TCHAR InitialProgram[MAX_PATH + 1];
BYTE EncryptionLevel;
ULONG ClientAddressFamily;
USHORT ClientAddress[CLIENTADDRESS_LENGTH + 1];
USHORT HRes;
USHORT VRes;
USHORT ColorDepth;
TCHAR ClientDirectory[MAX_PATH + 1];
ULONG ClientBuildNumber;
ULONG ClientHardwareId;
USHORT ClientProductId;
USHORT OutBufCountHost;
USHORT OutBufCountClient;
USHORT OutBufLength;
TCHAR DeviceId[MAX_PATH + 1];
} WTSCLIENT, *PWTSCLIENT;
This is my attempt so far:
[StructLayout( LayoutKind.Sequential )]
public struct _WTSCLIENT {
[MarshalAs( UnmanagedType.LPTStr )]
public String ClientName;
[MarshalAs( UnmanagedType.LPTStr )]
public String Domain;
[MarshalAs( UnmanagedType.LPTStr )]
public String UserName;
[MarshalAs( UnmanagedType.LPTStr )]
public String WorkDirectory;
[MarshalAs( UnmanagedType.LPTStr )]
public String InitialProgram;
public Byte EncryptionLevel;
public uint ClientAddressFamily;
[MarshalAsAttribute( UnmanagedType.ByValArray)]
public byte[] ClientAddress;
public ushort HRes;
public ushort VRes;
public ushort ColorDepth;
[MarshalAs( UnmanagedType.LPTStr )]
public String ClientDirectory;
public uint ClientBuildNumber;
public uint ClientHardwareId;
public ushort ClientProductId;
public ushort OutBufCountHost;
public ushort OutBufCountClient;
public ushort OutBufLength;
[MarshalAs( UnmanagedType.LPTStr )]
public String DeviceId;
}
I use it like this:
WTSQuerySessionInformation( serverHandle, si.SessionID, WTS_INFO_CLASS.WTSClientInfo, out clientInfoPtr, out bytes );
clientInfo = (_WTSCLIENT)Marshal.PtrToStructure( clientInfoPtr, typeof( _WTSCLIENT ) );
...but it bombs out silently, so obviously I have not matched the structure...
Can anyone help me with the struct conversion to C#
TIA...
--
Dag.

Try
[StructLayout(LayoutKind.Sequential)]
public struct WTSCLIENT
{
private const int CLIENTNAME_LENGTH = 20;
private const int DOMAIN_LENGTH = 17;
private const int USERNAME_LENGTH = 20;
private const int MAX_PATH = 260;
private const int CLIENTADDRESS_LENGTH = 30;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = CLIENTNAME_LENGTH + 1)]
public string ClientName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = DOMAIN_LENGTH + 1)]
public string Domain;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = USERNAME_LENGTH + 1)]
public string UserName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = MAX_PATH + 1)]
public string WorkDirectory;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = MAX_PATH + 1)]
public string InitialProgram;
public byte EncryptionLevel;
public uint ClientAddressFamily;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = CLIENTADDRESS_LENGTH + 1)]
public ushort[] ClientAddress;
public ushort HRes;
public ushort VRes;
public ushort ColorDepth;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = MAX_PATH + 1)]
public string ClientDirectory;
public uint ClientBuildNumber;
public uint ClientHardwareId;
public ushort ClientProductId;
public ushort OutBufCountHost;
public ushort OutBufCountClient;
public ushort OutBufLength;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = MAX_PATH + 1)]
public string DeviceId;
}
It should work. Its Marshal.SizeOf is the "right" one, both at 32 and 64 bits, both Ansi and Unicode.
If you are using the Unicode version of the methods change the first line to:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]

You could try the P/Invoke Interop Assistant

For your ULONG ClientBuildNumber; and all other ULONG s in C++, you have used the C# type uint. It could be an error that your definition of ULONG is a different size than uint.
Maybe you can try using ulong in C# (unsigned 64-bit, 0 to 18,446,744,073,709,551,615). This should match the standard Microsoft C++ ULONG definition.
MSDN C++
MSDN C# ulong

Another PInvoke - error message says source not found?

The struct that i have built in c# when run against the function does not give me one of the error message that tell me something is wrong with the struct. It says that a source file could not be found. Again, I don't know much about this DLL b/c of lack of documentation. But I am still thinking it is because I set the struct up wrong. Most likely i'm thinking the 3rd struct where it is referencing a struct within the struct.
i was hoping for some feedback on the work I did.
Thanks for the assistance.
This is what was provided in C:
int BatchTotal_Transactions(int transType, pTGiftCardReqBatchTotal req, pTGiftCardRespBatchTotal resp, int (*Com)(char *));
typedef struct _tagGiftCardReqBatchTotal
{
char Password[9];
char OperatorID[9];
char BatchNum[14];
char StartDate[11];
char EndDate[11];
unsigned char Type;
} TGiftCardReqBatchTotal, *pTGiftCardReqBatchTotal;
typedef struct _tagGiftCardRespBatchTotal
{
char Result;
char TerminalId[17];
unsigned char DispMsgControl;
char DispMsg[256];
char Display[41];
char Date[11];
char Time[9];
char RespCode[4];
char BatchNum[14];
char ErrorFlag;
char CustLang;
char UserLang;
char OpenDate[17];
char ClosedDate[17];
char StartDate[11];
char EndDate[11];
char BatchStatus;
int CardTypeNum;
TGiftCardTotals GctHost[MAX_CARD_CODES];
TGiftCardTotals GctTRS[MAX_CARD_CODES];
} TGiftCardRespBatchTotal, *pTGiftCardRespBatchTotal;
typedef struct _tagGiftCardTotals
{
unsigned short CardCode;
unsigned short PurchaseNum;
long PurchaseTotal;
unsigned short RefundNum;
long RefundTotal;
unsigned short RedemptionNum;
long RedemptionTotal;
unsigned short CorrectionNum;
long CorrectionTotal;
long PurchaseBenefitTotal;
long RefundBenefitTotal;
long RedemptionBenefitTotal;
} TGiftCardTotals, *pTGiftCardTotals;
And this is how I did it in C#:
[DllImport("batch.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Auto)]
public static extern int BatchTotal_Transactions(int transType, ref giftCardReqBatchTotal req, ref giftCardRespBatchTotal resp, IntPtr com);
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct _tagGiftCardReqBatchTotal
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 9)]
public string Password;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 9)]
public string OperatorID;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 14)]
public string BatchNum;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 11)]
public string StartDate;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 11)]
public string EndDate;
public byte Type;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct _tagGiftCardRespBatchTotal
{
public byte Result;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 17)]
public string TerminalId;
public byte DispMsgControl;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string DispMsg;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 41)]
public string Display;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 11)]
public string Date;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 9)]
public string Time;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string RespCode;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 14)]
public string BatchNum;
public byte ErrorFlag;
public byte CustLang;
public byte UserLang;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 17)]
public string OpenDate;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 17)]
public string ClosedDate;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 11)]
public string StartDate;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 11)]
public string EndDate;
public byte BatchStatus;
int CardTypeNum;
[MarshalAs(UnmanagedType.Struct, SizeConst = 1024)]
public _tagGiftCardTotals GctHost;
[MarshalAs(UnmanagedType.Struct, SizeConst = 1024)]
public _tagGiftCardTotals GctTRS;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct _tagGiftCardTotals
{
public UInt16 CardCode;
public UInt16 PurchaseNum;
public int PurchaseTotal;
public UInt16 RefundNum;
public int RefundTotal;
public UInt16 RedemptionNum;
public int RedemptionTotal;
public UInt16 CorrectionNum;
public int CorrectionTotal;
public int PurchaseBenefitTotal;
public int RefundBenefitTotal;
public int RedemptionBenefitTotal;
}

Are you sure the error isn't the following:
Specified module could not be found.
If this is the error then it is because the dll could not be found. Make sure the dll is in your path:
http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.dllimportattribute.value.aspx

passing char*[] from c++ dll Struct to c#

I'm trying to pass the following structure through c++ DLL to c#:
struct name
{ char* myArray[3];
char firstname[100];
char lastname[100];
};
void Caller(struct name * demo)
{
strcpy(demo->firstname,"hello");
demo->myArray[0]="hello";
demo->myArray[1]="hello";
demo->myArray[2]="hello";
ping(demo); //call to c# function
}
Below is my c# code:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct name
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
public string firstname;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
public string lastname;
//what should i marshal here for char* myArray[3];
} ;
static void Main(string[] args)
{
name myname = new name();
ping( ref myname);
}
public static void ping(int a,ref name myname)
{
Console.WriteLine(myname.firstname+"\n");
}
I am able to import first and last name from c++ dll.
What should I do to import char pointer array form c++?

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct Name
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
public string FirstName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
public string LastName;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
public string[] Array;
};
for my complete solution check Foo.cpp and Program.cs: https://gist.github.com/3779066