multi byte char * to csharp string

[caviar]

I'm trying to read in a ref parameter from a native dll, its working in vb
if i use the kernel32 functions below transforming the ref param to a vb
string:

Now, i want to skip this vb dll and use the native dll directly from c#
[DllImport("pafu tw32.dll")] // CharSet = CharSet.Auto, CallingConventi on
=CallingConvent ion.StdCall )]

public static extern short PAF_GetRecord(s hort listndx, short recno,
[MarshalAs(Unman agedType.LPWStr )]ref string pafrec, ref short pafreclen );

But whatever i try i cant read this ref string pafrec out, it will keep
empty or it has the length but it doenst show anything.. So, the thrick
should be in the MultiByteToWide char and MultiByteToUnic ode function..

So does anyone have an idea how to declare the DLLImport statement so it
will succesfully Marshall this _ref string pafrec_, which seems to be a
MultiByte string.

Regards h

************ori ginal c from the .h file

PREFIX short PASFIX PAF_GetRecord(s hort listndx, long recno,char *pafrec,
short pafreclen );

********* the vb helper functions.

Private Declare Function MultiByteToWide Char Lib "kernel32" (ByVal CodePage
As Long, ByVal dwFlags As Long, ByVal lpMultiByteStr As Long, ByVal
cchMultiByte As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As
Long) As Long

Public Function MultiByteToUnic ode(st As String, cpg As Long) As Variant

Dim stBuffer As String
Dim cwch As Long
Dim pwz As Long
Dim pwzBuffer As Long
Dim pwzBufferSize As Long
Dim b() As Byte

b = StrConv(st, vbFromUnicode)
pwz = VarPtr(b(0))
cwch = MultiByteToWide Char(cpg, 0, pwz, -1, ByVal 0&, ByVal 0&)

pwzBufferSize = cwch
stBuffer = String(pwzBuffe rSize, " ")
pwzBuffer = StrPtr(stBuffer )
cwch = MultiByteToWide Char(cpg, 0, pwz, -1, pwzBuffer,
pwzBufferSize)
MultiByteToUnic ode = Left(stBuffer, cwch - 1)

End Function

[Nicholas Paldino [.NET/C# MVP]]

caviar,

I'm assuming that the pafrec parameter is not allocated by the function,
and is a buffer that is passed into the function. The declaration you want
is:

[DllImport("pafu tw32.dll", CharSet=CharSet .Ansi)]
public static extern short PAF_GetRecord(
short listndx,
int recno,
[MarshalAs(Unman agedType.LPStr)] StringBuilder pafrec,
short pafreclen);

Your second parameter was being marshaled incorrectly. A long in C is
an int in C# (they are both 32 bits). Also, you need to use a StringBuilder
because you are expecting the value to change and you want to see that
change reflected.

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"caviar" <caviar-at-xsfourall.nl> wrote in message
news:eb******** ******@TK2MSFTN GP11.phx.gbl...

I'm trying to read in a ref parameter from a native dll, its working in vb
if i use the kernel32 functions below transforming the ref param to a vb
string:

Now, i want to skip this vb dll and use the native dll directly from c#
[DllImport("pafu tw32.dll")] // CharSet = CharSet.Auto, CallingConventi on
=CallingConvent ion.StdCall )]

public static extern short PAF_GetRecord(s hort listndx, short recno,
[MarshalAs(Unman agedType.LPWStr )]ref string pafrec, ref short pafreclen );

But whatever i try i cant read this ref string pafrec out, it will keep
empty or it has the length but it doenst show anything.. So, the thrick
should be in the MultiByteToWide char and MultiByteToUnic ode function..

So does anyone have an idea how to declare the DLLImport statement so it
will succesfully Marshall this _ref string pafrec_, which seems to be a
MultiByte string.

Regards h

************ori ginal c from the .h file

PREFIX short PASFIX PAF_GetRecord(s hort listndx, long recno,char *pafrec,
short pafreclen );

********* the vb helper functions.

Private Declare Function MultiByteToWide Char Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpMultiByteStr As Long, ByVal
cchMultiByte As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As
Long) As Long

Public Function MultiByteToUnic ode(st As String, cpg As Long) As Variant

Dim stBuffer As String
Dim cwch As Long
Dim pwz As Long
Dim pwzBuffer As Long
Dim pwzBufferSize As Long
Dim b() As Byte

b = StrConv(st, vbFromUnicode)
pwz = VarPtr(b(0))
cwch = MultiByteToWide Char(cpg, 0, pwz, -1, ByVal 0&, ByVal 0&)

pwzBufferSize = cwch
stBuffer = String(pwzBuffe rSize, " ")
pwzBuffer = StrPtr(stBuffer )
cwch = MultiByteToWide Char(cpg, 0, pwz, -1, pwzBuffer,
pwzBufferSize)
MultiByteToUnic ode = Left(stBuffer, cwch - 1)

End Function

[caviar]

"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard .caspershouse.c om> wrote in
message news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

caviar,

I'm assuming that the pafrec parameter is not allocated by the function, and is a buffer that is passed into the function. The declaration you want is:

[DllImport("pafu tw32.dll", CharSet=CharSet .Ansi)]
public static extern short PAF_GetRecord(
short listndx,
int recno,
[MarshalAs(Unman agedType.LPStr)] StringBuilder pafrec,
short pafreclen);

Your second parameter was being marshaled incorrectly. A long in C is
an int in C# (they are both 32 bits). Also, you need to use a StringBuilder because you are expecting the value to change and you want to see that
change reflected.

Hope this helps.

:-) Yes it did help!

Thank you very much!