Just wanted to post an update, I've been able to get "better" results by first casting the Value* to an inode:

INode* nodeTest = arg_list[0]->to_node();

INT_PTR nativePoint = (INT_PTR)(&(*(nodeTest)));

return IntegerPtr::intern(nativePoint);

However when I compare this address with the NativePointer address there is a 9 byte(?) difference. (e.g. c#: 764393721, C++: 764393712). Why is this the case? Would it be safe to juse 'offset' the C++ address? 

Thanks!

Final update ;) I solved it by not casting it to a node after all. Returning the IValue object memory address. Then in my C# Assembly I do the following with the address:

IValue value = global.Value.Marshal(new IntPtr(nodePointer));
IINode node = value.ToNode;

Incase there is a better way to do this I'd be happy to hear it! :)

Hey Marsel,

I’m wondering how stable my way  to pass MAXScript objects to my C# assembly is. I’m a bit worried the garbage collector might release the object and therefore making the address I get from C++ invalid. I’m not sure if this can ever happen because I’d still be holding a reference to my object so it probably wouldn’t be collected right?

This might not be an actual problem, but if I do this in Maxscript:

test = 5
GetMemoryAddress test
1117854848

memAddressTestWindow.MyTestMethod 1117854848

This works nicely, but then I change the address so it's no longer valid, I'm able to catch the exception the value.To... Method throws, but after this Max is sort of broken. If I try to print my variable test I get a *System exception* and when I run the GC I get a  "unknown error occured" messagebox. Do you know why this would be happening and if there is a way around this? 

Thanks in advance,
Vin

Hey Marsel, thanks for the reply! 

I thought the IValue would hang around until the object it wraps would be collected (oops!). However I'm a bit confused how I have to proceed now. Right now in C++ I return a pointer to an IValue and then pass this to the c# assembly to marshal it back to an IValue, to then call the .ToSomething methods. 

But if I understand correctly I should, from C++, return a pointer to for example a BitArray 

BitArray bitArray = arg_list[0]->to_Bitarray();
INT_PTR nativePoint = (INT_PTR)(&(bitArray));

and then pass that pointer to C# but how would I then marshal that pointer back to an IBitArray? IBitArray doesn't have the .Marshal method. 

 EDIT: I've checked a few more interfaces now that I got home and almost none of them have a Marshal method. (IMesh, IPoint3,...)

EDIT2: I've changed my C++ extension method now as a test to return the address of an Mesh object instead of a Value wrapper object:

Mesh* mesh = arg_list[0]->to_mesh();
INT_PTR testAddress = (INT_PTR)&(*(mesh));

I've compared this address to the one I can get from C# and it's the same. 

var node = GlobalInterface.Instance.COREInterface.GetSelNode(0);
ITriObject triObj = node.ObjectRef.FindBaseObject() as ITriObject;
IMesh mesh = triObj.Mesh;
IntPtr meshPtr = mesh.NativePointer; //same as my C++ pointer - so it's correct

This is just a test of course, I don't want to select the object in my assembly, I'd like to pass a mesh object to it instead. But how would I marshal this pointer to an IMesh object? 

Hey Marsel,

Sorry to keep bumping this, but I’m a bit lost here. I’m trying to store a pointer to the data the Value object is wrapping rather than a pointer to the Value (because of what you said). However,  I’m not even sure how to get a pointer for the wrapped objects.

//Get the Point3 value the Value* object is wrapping
Point3 value = arg_list[0]->to_point3();

“value” is just a new object on the stack so I can’t take the address of that one as it’ll go out of scope after this method call.
I’ve tried to change (but probably shouldn’t) the “to_point3” method from:

virtual Point3 to_point3() { ABSTRACT_CONVERTER(Point3, Point3); }

to

virtual Point3* to_point3_2() { ABSTRACT_CONVERTER(Point3*, Point3); }

The X and Y properties are correct but Z is always zero, but I’m not sure if I can just change the methods like that.

Do you know how I could get a pointer to the object the value object is wrapping around?

Thanks in advance,
Vin

Hey Marsel,

Thanks! So I can store a Value object that is wrapping a point3/int/etc., wouldn't the Value object still be managed by MAXScript? The main goal was to pass MAXScript Point3 values to C#. I get the Value* and then pass that to C#, marshal it back to an IValue and then call .ToPoint3(), is this valid for simple types like that?

For INodes I'd store the Node pointer and marshal that one in C#, instead of the Value*.

Thanks again,
Vin

Thanks a lot for all your help! I won't be storing a Value*! :)

One last question, how would I send a simple object like Point3 from MAXScript to C#? I assume the easiest would be to just pass the 3 values? (Gets a bit tricky with BitArray then I would think...).

For more complex objects I'll use the to_... Methods and store that pointer and marshal it in C# to the correct type. 

mxsValue being a IValue object correct? How would I get this object without storing a pointer to it from in C++ and then marshalling it in C# to a IValue object. 

Originally I had this:

C++: Return the Value*
MXS: Pass the Value* to C# assembly
C#: Marshal Value* to IValue object. Use one of the to_... methods like you just showed to get the object.

Is there another way to pass an IValue object from MXS directly to C#, without the C++ in between? I've tried having an IValue object as parameter like this: 

public void Test(Ivalue valueObject) 

and then using the .to methods on that one, but it doesn't work in MAXScript:

myPoint = [5,5,5]
[5,5,5]
myAssembly.Test myPoint
-- Runtime error: No method found which matched argument list

Thanks! Although the bad part would be that the Value* could become invalid between calls (C++ and C#), when it gets collected by MAXScript potentially. 

Anyway, thanks for all the help with this!

But in theory it could be called between these 2 calls?:

myValuePointer = GetMemoryAddress myPoint --get the memory address of the Value object wrapper around myPoint

MXS GC?

MyCSharpAssembly.SomeMethod myValuePointer --this one will marshal the address to IValue object

Aha! That clears a lot up about the garbage collector. Thanks a lot for all the info! :)