How to use pinvoke to marshall structure inside another passed to C DLL

Question

I am trying to figure out how to embed a simple structure inside another structure that is passed to a C dll from c#. How do you marshall the embedded structure? Stripped down to essentials.

//The C code
typedef struct {
       int a;
       int b;
} A;
typedef struct {
      int c;
      A myStruct;
} B;

//The c# code:
using System.Runtime.InteropServices;

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    public class A{
        int a;
        int b;
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    public class B{
          int c;
          public IntPtr A;
     }

Answer 1

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class B{
      int c;
      public A a;
    }

You need IntPtr only if B is defined as:

typedef struct {
      int c;
      A* myStruct;
} B;