I have a C++ dll which returns a structure, the structure
contains a char[21] variable, as shown below.

struct MyCStruct
{
    short iNumber;
    char Name[21];
};

I've declared a structure in C# as shown below

[StructureLayout[LayoutKind.Sequential)]
class MyCSharpStruct
{
    short iNumber;
    char[] Name;
}

when I call my dll function I pass the structure as a
LPStruct as shown below

[DllImport]
unsafe static extern bool MyDllFunction(short* iNumber,
[MarshalAs(UnmanagedType.LPStruct)]MyCSharpStruct
myStructure);

when I call this function (from an unsafe code block)

short iNumber = 1;
MyCSharpStruct myStructure = new MyCSharpStruct();
MyDllFunction(&iNumber,myStructure);

I get the error "Object reference is not set to an
instance of an object". What am I doing wrong? If I take
the char[21] element out of my C++ structure and my C#
class and call the dll everything works OK so I'm sure it
the char[] that causes the problem. Is it because char in
C# is 16bit? I added CharSet = CharSet.Ansi to the
DllImport but it doesn't make any difference. Is it
because I have to initialise the C# char array? Where do
I have to do this?