Marshaling a C++ two-dimensional fixed length char array as a structure member

Question

I am trying to call an unmanaged C++ function, that has a structure as an input parameter. The structure is defined in the header file like this:

struct MySt         


        

Answer 1

Try using multiple C# structs:

[StructLayoutAttribute(LayoutKind.Sequential, CharSet=CharSet.Ansi)]
public struct MyStruct_Name
{
    [MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 25)]
    public string name;
}

[StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct MyStruct
{
    public int siOrder;

    [MarshalAsAttribute(UnmanagedType.ByValArray, SizeConst = 6)]
    public MyStruct_Name aaszNames;

    [MarshalAsAttribute(UnmanagedType.ByValArray, SizeConst = 6, ArraySubType = UnmanagedType.I4)]
    public int[] siId;

    [MarshalAsAttribute(UnmanagedType.ByValArray, SizeConst = 6, ArraySubType = UnmanagedType.I4)]
    public int[] siTones;
}

This is how I've been passing arrays of C-style strings around.

Don't forget to create the contents of aaszNames! The marshaller hates null references.

MyStruct foo = new MyStruct();
for (int i = 0; i < 6; i++)
{
    foo.aaszNames[i] = new MyStruct_Name();
    foo.aaszNames[i].name = "";
}

Good luck!

Answer 2

char aaszNames[6][25];

char of C++ Type is 8 bits~

but char of C# Type is Unicode ,(16 bits) !

so char of C++ Type <-> byte of C# type

Answer 3

I would write a small c-program to check the byte size of the C-structure.
Then I would go with the other suggestion to extract the data field by field.
From a C standpoint the /0 is treated as normal character included in the 6 bytes whereas C# would use a length of 5 and have the /0 hidden.

Answer 4

[MarshalAsAttribute(UnmanagedType.ByValArray, SizeConst=150)]
 public char[] aaszNames;

That marshalling type looks well. Probably issue in function call, or bad memory allocation/