P/Invoke returning and passing bool's between C# and C++

[Philippe F. Bertrand]

Summary - What should a C# bool map to in C++? Are return types
different?

I have lots of methods declared with bool parameters and bool return
type which appear to work without any problems but one method in
particular seems to always return true.

The method is declared in C# as

[DllImport("my.d ll")] private static extern
bool T_Cursor_GetBoo lean(
int key, short columnID, ErrorCode *code
);

And in C++ as

extern "C" {
__declspec(dlle xport) bool T_Cursor_GetBoo lean(
int natKey, short cid, int *code
);
}

__declspec(dlle xport) bool T_Cursor_GetBoo lean(
int natKey, short cid, int *code
)
{
bool out = some stuff;
return out;
}

Stepping through the code in Visual Studio on the desktop, I see the
unmanaged code returning false and the managed code receiving true.

I need this code to work on both the .NET framework and the
CompactFramewor k.

Is there a way to globally change the marshalling of bool's and will
this work in the compact framework?

- Thanks
Philippe

[Mattias Sjögren]

Philippe,

Summary - What should a C# bool map to in C++? Are return types
different?

Depends on your marshaling settings.

The default is a 32-bit Win32 BOOL.
With [MarshalAs(Unama ngedType.Varian tBool)] you get a 16-bit
VARAIANT_BOOL.
With [MarshalAs(Unama ngedType.I1)] you get a one byte C++ bool (or
Win32 BOOLEAN).

So in your case, I'd try to change the declaration to

[DllImport("my.d ll")]
[return: MarshalAs(Unman agedType.I1)]
private static extern bool T_Cursor_GetBoo lean( ...
That's how it works on the desktop CLR anyway. I'm not familiar enough
with .NET CF to say how it works there.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.

[Chris Tacke, eMVP]

In the CF there's no COM interop, so it's always 32-bits. Use an int.

--
Chris Tacke, eMVP
Advisory Board Member
www.OpenNETCF.org
---
Windows CE Product Manager
Applied Data Systems
www.applieddata.net

"Philippe F. Bertrand" <pf***@yahoo.ca > wrote in message
news:dd******** *************** ***@posting.goo gle.com...

Summary - What should a C# bool map to in C++? Are return types
different?

I have lots of methods declared with bool parameters and bool return
type which appear to work without any problems but one method in
particular seems to always return true.

The method is declared in C# as

[DllImport("my.d ll")] private static extern
bool T_Cursor_GetBoo lean(
int key, short columnID, ErrorCode *code
);

And in C++ as

extern "C" {
__declspec(dlle xport) bool T_Cursor_GetBoo lean(
int natKey, short cid, int *code
);
}

__declspec(dlle xport) bool T_Cursor_GetBoo lean(
int natKey, short cid, int *code
)
{
bool out = some stuff;
return out;
}

Stepping through the code in Visual Studio on the desktop, I see the
unmanaged code returning false and the managed code receiving true.

I need this code to work on both the .NET framework and the
CompactFramewor k.

Is there a way to globally change the marshalling of bool's and will
this work in the compact framework?

- Thanks
Philippe