using System;

using System.Runtime.InteropServices;

​

[StructLayout(LayoutKind.Sequential, Pack = 1)]

struct TestStruct

{

    public byte a;

    public byte b;

    public byte c;

    public byte d;

}

​

[StructLayout(LayoutKind.Explicit)]

struct TestContainer

{

    [FieldOffset(0)]

    public uint v;

    [FieldOffset(0)]

    public TestStruct s;

}

public class Program

{

    public static void Main()

    {

        TestContainer c = default;

        c.v = 0xddccaabb;

        Console.WriteLine($"{c.v:x8} {c.s.a:x2} {c.s.b:x2} {c.s.c:x2} {c.s.d:x2}");

        c.s.b = 0xff;

        c.s.d = 0xff;

        Console.WriteLine($"{c.v:x8} {c.s.a:x2} {c.s.b:x2} {c.s.c:x2} {c.s.d:x2}");

    }

}