Help on calling DLL

[caperover2000]

Hi, All,

I have a third party dll, which has been used in C#, and now I want to call it from native C++. I am have some troubling making it work. Could you someone please help?

Two functions are defined and used in C# as follows:

[DllImport(strDllFile, CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode)]
public static extern int FT_ifinDLogin(string strUserName, string strPassWord, int nType);

[DllImport(strDllFile, CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode)]
unsafe public static extern int FTQueryTHS_SynHisQuoteC(string THSCodes,
string jsonIndicator,
string jsonParam,
string begintime,
string endtime,
out char* pret
);

static int THS_iFinDLogin(string account, string password)
{
return FT_ifinDLogin(account, password, 5);
}

unsafe static string THS_HistoryQuotes(string THSCodes,
string jsonIndicator,
string jsonParam,
string begintime,
string endtime
)
{
string strOut;
char* Pret;
FTQueryTHS_SynHisQuoteC(THSCodes, jsonIndicator, jsonParam, begintime, endtime, out Pret);
IntPtr data = new IntPtr(Pret);
strOut = Marshal.PtrToStringUni(data);
DeleteBuffer(Pret);
return strOut;
}


In C++, I define the functions as follows

typedef int (__stdcall *THS_IFinDLogin)(const wchar_t *, const wchar_t *, int)

typedef int (__stdcall *THS_HistoryQuotes( const wchar_t *, const wchar_t *,const wchar_t *,const wchar_t *,const wchar_t *, wchar_t *)

When calling them in C++, it always fails with an error "wrong request data".

Could anyone help me out?

Thanks!

CR

[2kaud]

I'm by no means an expert on c#, but in c# I understand that a string consists of a sequential collection of Char objects together with a Length property that represents the number of Char objects it contains, not the number of Unicode characters.

This is completely different from c++. I think the answer in c++ is to use BSTR.

See https://www.codeproject.com/articles...ng-conversions

which although is for VB I think is also valid for c#.

[caperover2000]

Thanks for your suggestion. My understanding is that BSTR should be used when calling COM components, but the dll does not look like COM but native C functions instead.

C# explicitly specify the Char Set as Unicode. I tend to think that is where the problem might be.

[Arjay]

Frome the command line, do a dumpbin /exports on the dll and see what the exported function signatures are.

[caperover2000]

dumpbin /exports does not tell all the information especially if a short alias is defined.
I know the C# code is working fine and just want to figure out a way to replicate it in C++.

[Arjay]

dumpbin /exports does not tell all the information especially if a short alias is defined.
I know the C# code is working fine and just want to figure out a way to replicate it in C++.

Do you know whether the dll is coded for ANSI or UNICODE? Looks probably to be UNICODE.
Check out pinvoke.net for conversion ideas (the site will have examples of native c functions converted to c#. You can find similar params in c" and look at their native counterparts.