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passing a struct by ref to unmanged code

i want to pass a struct by reference to a function in a c++ dll.

the problem is that the call causes an ArgumentExcepti on in the calling c#
code.
i already tried to use "out" instead of "ref" there was no exception
generated but i
saw in the unmanaged code all fields of the struct were uninitialized!
this is my c# code:

[StructLayout(La youtKind.Sequen tial,Pack=1)]
struct WorldStats
{
public ObjectStats[] stats;
public int iterations;
public int living;
public WorldStats(int n)
{
stats = new ObjectStats[n];
iterations=0;
living=0;
}
}

[DllImport("aike rnel.dll", CallingConventi on=CallingConve ntion.Winapi)]
static extern void GetWorldStats(r ef WorldStats ws);

WorldStats ws = new WorldStats(this .MAXOBJECTS);
GetWorldStats(r ef ws); // here is the argumentexcepti on thrown
the function in my c++ dll is declared as follows:
__declspec(dlle xport) void /*WINAPI*/__stdcall GetWorldStats(W orldStats &
ws);

#pragma pack(push,1)
struct WorldStats
{
ObjectStats * stats;
int iterations;
int living;
};
#pragma pack(pop,1)

--
cody

[Freeware, Games and Humor]
www.deutronium.de.vu || www.deutronium.tk

Jul 21 '05 #1
1 1848
[StructLayout(La youtKind.Sequen tial,Pack=1)]
struct WorldStats
{
public ObjectStats[] stats;
public int iterations;
public int living;

The exception is likely caused by the stats member. You can't declare
it as an array, it will not marshal correctly. Try making it an IntPtr
instead, and handle the array allocation and initialization yourself.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.
Jul 21 '05 #2

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