Marshaling Multi-Dimensional Arrays

[Thomas Kent]

I have a dll that is expecting a 3x3 array which I'm am using DllImport to access. In addition, this array is located in a struct that is getting passed. I'm having problems that I think are located somewhere in how I'm marshaling it. Any input would be appreciated.
(examples are shortened for clarity, let me know if something more complete would be useful

/*C code*
typedef float RotMtxType[3][3]
typedef struct
double ccNum
RotMtxType ccuGCCtoLNEDrot Mtx;
extern int ccuInitStateStr ucture
CCUStateStruct *ccuStatePtr)

//C# Cod
[StructLayout(La youtKind.Sequen tial)
public struct CCUStateStruc
public double ccNum
[MarshalAs(Unman agedType.ByValA rray, SizeConst=9
public float [,] ccuGCCtoLNEDDro tMtx
elsewhere ..
ccuState.ccuGCC toLNEDDrotMtx = new float[3,3
...

[DllImport("CCU. dll")
public extern static int ccuInitStateStr ucture
[MarshalAs(Unman agedType.Struct )]ref CCUStateStruct ccuStatePtr)

I then get the error
Additional information: Can not marshal field ccuGCCtoLNEDrot Mtx of type CCUStateStruct: This type can not be marshaled as a structure field

Thanks much
To

[John Wood]

If you declare ccuGCCtoLNEDDro tMtx as a single dim array, does that work?
Could you add some property get/sets to expose the single dim array as a two
dim array?

"Thomas Kent" <te*****@commun ity.nospam> wrote in message
news:14******** *************** ***********@mic rosoft.com...

I have a dll that is expecting a 3x3 array which I'm am using DllImport to access. In addition, this array is located in a struct that is getting
passed. I'm having problems that I think are located somewhere in how I'm
marshaling it. Any input would be appreciated. (examples are shortened for clarity, let me know if something more complete would be useful)
/*C code*/
typedef float RotMtxType[3][3];
typedef struct {
double ccNum;
RotMtxType ccuGCCtoLNEDrot Mtx;
}

extern int ccuInitStateStr ucture(
CCUStateStruct *ccuStatePtr);

//C# Code
[StructLayout(La youtKind.Sequen tial)]
public struct CCUStateStruct
{

public double ccNum;
[MarshalAs(Unman agedType.ByValA rray, SizeConst=9]
public float [,] ccuGCCtoLNEDDro tMtx;
}

elsewhere ...
ccuState.ccuGCC toLNEDDrotMtx = new float[3,3]
...

[DllImport("CCU. dll")]
public extern static int ccuInitStateStr ucture (
[MarshalAs(Unman agedType.Struct )]ref CCUStateStruct ccuStatePtr);
I then get the error:
Additional information: Can not marshal field ccuGCCtoLNEDrot Mtx of type CCUStateStruct: This type can not be marshaled as a structure field.

Thanks much!
Tom

[Jeffrey Tan[MSFT]]

Hi Tom,

Based on my understanding, you want to P/invoke a Structure with a field of
Multi-Dimensional array.

For your issue, you may use single dimensional C# array to store the value
and marshal to your dll. Do like this:

[StructLayout(La youtKind.Sequen tial)]
public struct CCUStateStruct
{
public double ccNum;
[MarshalAs(Unman agedType.ByValA rray, SizeConst=9)]
public float [] ccuGCCtoLNEDDro tMtx;
}

Then, you can use it like:
try
{
CCUStateStruct obj=new CCUStateStruct( );
obj.ccNum=0.0;
float [] test=new float[9];

obj.ccuGCCtoLNE DDrotMtx=test;
ccuInitStateStr ucture(ref obj);
}
catch(Exception ex)
{
MessageBox.Show (ex.Message);
}

I have tested this on my machine, it works well.

=============== =============== =====
Please apply my suggestion above and let me know if it helps resolve your
problem.

Thank you for your patience and cooperation. If you have any questions or
concerns, please feel free to post it in the group. I am standing by to be
of assistance.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.