Marshalling string to PWSTR

microsoft.public.dotnet.framework

29 Nov 2006 11:41 AM

Roshan

Hi List,

I am trying to call a method from a native DLL which takes a PWSTR as
an input param. From my managed code (C#), I want to pass a string as a
parameter. How do I convert a C# string to a PWSTR?

Currently I am using

[DllImport("Some.dll", SetLastError = true, CharSet = CharSet.Unicode,
EntryPoint = "SomeMethod")]
public static extern bool SomeMethod(IntPtr fileName); //PWSTR

and calling as

string str = "roshan";
bool val = SomeMethod(Marshal.StringToHGlobalAnsi(str));

My native method has the signature

bool SomeMethod(PWSTR fileName)

If I print the received value using printf it works fine, but when I
use it as a parameter to some Win32 APIs it fails. The problem seems to
be that I am converting the string to an ANSI string and not unicode
/wide char (PWSTR) that the native method expects.

Using Marshal.StringToHGlobalAuto() & Marshal.StringToHGlobalUni()
don't work.

Any help is greatly appreciated.

Thanks,
Roshan

29 Nov 2006 2:04 PM

Vadym Stetsyak

Hello, Roshan!

Try

[DllImport("Some.dll", SetLastError = true, CharSet =
CharSet.Unicode,
EntryPoint = "SomeMethod")]
public static extern bool SomeMethod(([MarshalAs(LPWStr)] string fileName);

R> I am trying to call a method from a native DLL which takes a PWSTR as
R> an input param. From my managed code (C#), I want to pass a string as
R> a
R> parameter. How do I convert a C# string to a PWSTR?

R> Currently I am using

R> [DllImport("Some.dll", SetLastError = true, CharSet =
R> CharSet.Unicode,
R> EntryPoint = "SomeMethod")]
R> public static extern bool SomeMethod(IntPtr fileName);
R> //PWSTR

R> and calling as

R> string str = "roshan";
R> bool val = SomeMethod(Marshal.StringToHGlobalAnsi(str));

R> My native method has the signature

R> bool SomeMethod(PWSTR fileName)

R> If I print the received value using printf it works fine, but when I
R> use it as a parameter to some Win32 APIs it fails. The problem seems
R> to
R> be that I am converting the string to an ANSI string and not unicode
R> /wide char (PWSTR) that the native method expects.

R> Using Marshal.StringToHGlobalAuto() & Marshal.StringToHGlobalUni()
R> don't work.

R> Any help is greatly appreciated.

R> Thanks,
R> Roshan

--
Regards, Vadym Stetsyak
www: http://vadmyst.blogspot.com

30 Nov 2006 4:51 AM

Roshan

Hi Vadym,

I already tried using [MarshalAs(UnmanagedType.LPWStr)]. It doesn't
work. In my native DLL if I print the parameter using printf, I get
just the first character.

Regards,
Roshan

Vadym Stetsyak wrote:
Show quote

> Hello, Roshan!
>
> Try
>
> [DllImport("Some.dll", SetLastError = true, CharSet =
> CharSet.Unicode,
> EntryPoint = "SomeMethod")]
> public static extern bool SomeMethod(([MarshalAs(LPWStr)] string fileName);
>
>
> R> I am trying to call a method from a native DLL which takes a PWSTR as
> R> an input param. From my managed code (C#), I want to pass a string as
> R> a
> R> parameter. How do I convert a C# string to a PWSTR?
>
> R> Currently I am using
>
> R> [DllImport("Some.dll", SetLastError = true, CharSet =
> R> CharSet.Unicode,
> R> EntryPoint = "SomeMethod")]
> R> public static extern bool SomeMethod(IntPtr fileName);
> R> //PWSTR
>
> R> and calling as
>
> R> string str = "roshan";
> R> bool val = SomeMethod(Marshal.StringToHGlobalAnsi(str));
>
> R> My native method has the signature
>
> R> bool SomeMethod(PWSTR fileName)
>
> R> If I print the received value using printf it works fine, but when I
> R> use it as a parameter to some Win32 APIs it fails. The problem seems
> R> to
> R> be that I am converting the string to an ANSI string and not unicode
> R> /wide char (PWSTR) that the native method expects.
>
> R> Using Marshal.StringToHGlobalAuto() & Marshal.StringToHGlobalUni()
> R> don't work.
>
> R> Any help is greatly appreciated.
>
> R> Thanks,
> R> Roshan
>
>
> --
> Regards, Vadym Stetsyak
> www: http://vadmyst.blogspot.com

30 Nov 2006 9:12 AM

Vadym Stetsyak

Hello, Roshan!

printf() is used to print ANSI strings, since you're passing UNICODE string
then you have to use wprintf(...);

R> I already tried using [MarshalAs(UnmanagedType.LPWStr)]. It doesn't
R> work. In my native DLL if I print the parameter using printf, I get
R> just the first character.

R> Regards,
R> Roshan

R> Vadym Stetsyak wrote:
Show quote

>> Hello, Roshan!

>> Try

>> [DllImport("Some.dll", SetLastError = true, CharSet =
>> CharSet.Unicode,
>> EntryPoint = "SomeMethod")]
>> public static extern bool SomeMethod(([MarshalAs(LPWStr)] string
>> fileName);

>> R> I am trying to call a method from a native DLL which takes a PWSTR
>> as
>> R> an input param. From my managed code (C#), I want to pass a string
>> as
>> R> a
>> R> parameter. How do I convert a C# string to a PWSTR?

>> R> Currently I am using

>> R> [DllImport("Some.dll", SetLastError = true, CharSet =
>> R> CharSet.Unicode,
>> R> EntryPoint = "SomeMethod")]
>> R> public static extern bool SomeMethod(IntPtr fileName);
>> R> //PWSTR

>> R> and calling as

>> R> string str = "roshan";
>> R> bool val = SomeMethod(Marshal.StringToHGlobalAnsi(str));

>> R> My native method has the signature

>> R> bool SomeMethod(PWSTR fileName)

>> R> If I print the received value using printf it works fine, but when
>> I
>> R> use it as a parameter to some Win32 APIs it fails. The problem
>> seems
>> R> to
>> R> be that I am converting the string to an ANSI string and not
>> unicode
>> R> /wide char (PWSTR) that the native method expects.

>> R> Using Marshal.StringToHGlobalAuto() & Marshal.StringToHGlobalUni()
>> R> don't work.

>> R> Any help is greatly appreciated.

>> R> Thanks,
>> R> Roshan

>> --
>> Regards, Vadym Stetsyak
>> www: http://vadmyst.blogspot.com

--
Regards, Vadym Stetsyak
www: http://vadmyst.blogspot.com

30 Nov 2006 12:23 PM

mehr13

Try declaring the C++ function param as BSTR;

bool SomeMethod(BSTR fileName);

[DllImport("Some.dll", SetLastError = true, CharSet =
CharSet.Unicode,
EntryPoint = "SomeMethod")]
public static extern bool SomeMethod(([In,
MarshalAs(UnmanagedType.BStr)] string fileName);

MH

Roshan wrote:
Show quote

> Hi Vadym,
>
> I already tried using [MarshalAs(UnmanagedType.LPWStr)]. It doesn't
> work. In my native DLL if I print the parameter using printf, I get
> just the first character.
>
> Regards,
> Roshan
>
> Vadym Stetsyak wrote:
> > Hello, Roshan!
> >
> > Try
> >
> > [DllImport("Some.dll", SetLastError = true, CharSet =
> > CharSet.Unicode,
> > EntryPoint = "SomeMethod")]
> > public static extern bool SomeMethod(([MarshalAs(LPWStr)] string fileName);
> >
> >
> > R> I am trying to call a method from a native DLL which takes a PWSTR as
> > R> an input param. From my managed code (C#), I want to pass a string as
> > R> a
> > R> parameter. How do I convert a C# string to a PWSTR?
> >
> > R> Currently I am using
> >
> > R> [DllImport("Some.dll", SetLastError = true, CharSet =
> > R> CharSet.Unicode,
> > R> EntryPoint = "SomeMethod")]
> > R> public static extern bool SomeMethod(IntPtr fileName);
> > R> //PWSTR
> >
> > R> and calling as
> >
> > R> string str = "roshan";
> > R> bool val = SomeMethod(Marshal.StringToHGlobalAnsi(str));
> >
> > R> My native method has the signature
> >
> > R> bool SomeMethod(PWSTR fileName)
> >
> > R> If I print the received value using printf it works fine, but when I
> > R> use it as a parameter to some Win32 APIs it fails. The problem seems
> > R> to
> > R> be that I am converting the string to an ANSI string and not unicode
> > R> /wide char (PWSTR) that the native method expects.
> >
> > R> Using Marshal.StringToHGlobalAuto() & Marshal.StringToHGlobalUni()
> > R> don't work.
> >
> > R> Any help is greatly appreciated.
> >
> > R> Thanks,
> > R> Roshan
> >
> >
> > --
> > Regards, Vadym Stetsyak
> > www: http://vadmyst.blogspot.com