Pinvoke String problem

[Marco Mariv via DotNetMonster.com]

Hi group,

i have a problem.
I don't succeded to pass string from Unmanaged Code to managed code.
I have this situation:

Unmanaged Code:
------------------------
DRIVER_API int __stdcall
Read (LPWSTR data,int *len,int *lenwct)
{
..
...
....
char lpstr[255];
wchar_t szTmp[255];
..
...
....

*len = strlen(lpstr);
*lenwct = wcstombs(lpstr,szTmp,255);
..
...
....
return 1;

}

Managed Code (VB.NET):
------------------------
<DllImport("MyDriver.dll", EntryPoint:="Read", CallingConvention:=CallingConvention.Winapi, SetLastError:=True)> _
PublicFunction Read(ByVal data As StringBuilder, ByRef len As Int64,ByRef lenwct As Int64) As Integer
End Function

-------
When i (p)invoke this function i have this responce:
len = 120
lenwct = 6
data ="??????||||||"

why?

I dont' know how to convert a string (char *) to LPWSTR.
How can i pass a string from Unmenaged to menaged code.

I have use StringBuilder. Is it a correct solution?

Help me!

 

[Sergey Bogdanov]

EVC "int" type represents Int32 for CF.NET instead of Int64 (see
Blittable Types table [1]). Also did you initialize StringBuilder before
invoke Read method?

Dim data As New StringBuilder(MAX_PATH)
ret = Read(data, len, lenwct)

And one more thing instead of wcstombs use:

mbstowcs(szTmp, lpstr, 255);

[1]
http://msdn.microsoft.com/library/en-us/dnnetcomp/html/netcfintrointerp.asp

Hope this help,
Sergey Bogdanov
http://www.sergeybogdanov.com

 

[Marco Mariv via DotNetMonster.com]

Thanks for reply!

I have found the problem!!!
The Pocket PC generally requires character string parameters to be in Unicode, not in single byte character.

Visit the page:
http://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/dnarppc2k/html/ppc_ode.asp

So first to pass the string i have to use this function:

ConvertCToT(TCHAR* pszDest, const CHAR* pszSrc)
{
for(int i = 0; i < strlen(pszSrc); i++)
pszDest = (TCHAR) pszSrc;
}

So it's ok!