Paasing structs to/from C# via MC++ to C++ dll - How?

[Keith M]

Hi,

I am a bit of a newcomer to C# but have experience with (unmanaged) C++.

Now, I have a 3rd party dll and headers. This dll is a C++ style dll that
exports classes and structs.
I am attempting to write a Managed C++ wrapper dll for this dll in order
that it can be used from various C# modules in the overall project.
The managed C++ project can 'see' the definitions for the structs that the
lower functions use in the supplied headers.

I cannot reference these headers from the C# project (and have a feeling
that even if I could it would be a 'bad thing' to do so). So how do I
export wrapper structs from the middle tier managed c++ dll to the upper C#
level and how do I convert and pass them up and down the chain?

Hope this query makes sense. Many thanks

--
KM

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

Keith,

It all depends on the structure actually. Depending on how complex it
is, perhaps you want to create a class representation (in managed code), and
then handle the conversion somewhere in the MC++ code. Can you show the
structure that you want to define/use?
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Keith M" <ke***********@nospam.amsjv.com> wrote in message
news:3f********@baen1673807.greenlnk.net...

Hi,

I am a bit of a newcomer to C# but have experience with (unmanaged) C++.

Now, I have a 3rd party dll and headers. This dll is a C++ style dll that
exports classes and structs.
I am attempting to write a Managed C++ wrapper dll for this dll in order
that it can be used from various C# modules in the overall project.
The managed C++ project can 'see' the definitions for the structs that the
lower functions use in the supplied headers.

I cannot reference these headers from the C# project (and have a feeling
that even if I could it would be a 'bad thing' to do so). So how do I
export wrapper structs from the middle tier managed c++ dll to the upper C# level and how do I convert and pass them up and down the chain?

Hope this query makes sense. Many thanks

--
KM

[Keith M]

"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard.caspershouse.com> wrote in
message

It all depends on the structure actually. Depending on how complex it
is, perhaps you want to create a class representation (in managed code), and then handle the conversion somewhere in the MC++ code. Can you show the
structure that you want to define/use?

Here is a typical one of about 10 that I have:

typedef struct _MYStruct{
LARGE_INTEGER CreationTime;
LARGE_INTEGER LastAccessTime;
LARGE_INTEGER LastWriteTime;
ULONG FileAttributes;
ULONG NumVersions;
ULONG NumFragments;
ULONG Flags;
USHORT ExtraHeaderSize;
USHORT ExtraFooterSize;
} MyStruct;

Any ideas welcome! What a wrapper class would look like and how to convert?
The LARGE_INTEGER member is actually a WIn32 defined structure or union so
how would I incorporate this?
I am thinking I will have to write a series of conversion functions, one for
each struct I want to use and simply do a member wise copy in the function.
As for the large int structure I think I will have to define my own similar
struct and use this in my new wrapper class.

Thanks

[Mattias Sjögren]

Keith,

What a wrapper class would look like and how to convert?
Something like

__value struct MyManagedStruct {
Int64 CreationTime;
Int64 LastAccessTime;
Int64 LastWriteTime;
UInt32 FileAttributes;
UInt32 NumVersions;
UInt32 NumFragments;
UInt32 Flags;
UInt16 ExtraHeaderSize;
UInt16 ExtraFooterSize;
};

The LARGE_INTEGER member is actually a WIn32 defined structure or union so
how would I incorporate this?
Work with the QuadPart member of the union, it's just a 64-bit
integer. You should be able to assign it to/from a System::Int64.

I am thinking I will have to write a series of conversion functions, one for
each struct I want to use and simply do a member wise copy in the function.

Yes, that will work. But for simple integer data like the struct
above, you could also just to a memcpy between the native and managed
structs.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
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