结构体成员定义的顺序也会影响结构体的大小，内存对齐，内存填充

using System;
using System.Runtime.InteropServices;

struct StrcutOne
{
    public int b; // 4 bytes
    public byte a; // 1
    public byte c; // 1
    // 4+1+1+2(在填充两个2个字节) = 8 字节
}

struct StrcutTwo
{
    public byte a; // 1 byte
    public int b; // 4 bytes
    public byte c; // 1 byte
    // 1+3(填充)+4+1+3(填充) = 12
}

class Program
{
    static void Main()
    {
        Console.WriteLine($"Size of ChangedOrder: {Marshal.SizeOf<StrcutOne>()} bytes");
        Console.WriteLine($"Size of ExampleStruct: {Marshal.SizeOf<StrcutTwo>()} bytes");
    }
}