CSharp中Struct内存大小

sizeof 只适用于值类型，并且需要在unsafe上下文环境中使用
也可以使用 System.Runtime.InteropServices.Marshal.SizeOf()

• 新建C#控制台项目，项目设置 unsafe 允许不安全代码
  

Program.cs

using System;

namespace test
{
    class Program
    {
        public struct A //size 8=a(4)+b(4)
        {
            public char a;
            public int b;
        }
        public unsafe struct B  //size 12=a(4)+b(4)+c(4)
        {
            public char a;
            public int b;
            public byte c;
        }

        public struct C //size 8=a(2)+c(2)+b(4)
        {
            public char a;

            public byte c;
            public int b;
        }

        public struct D //size 2=a(2)
        {
            public char a;
        }

        static void Main(string[] args)
        {
            TestSize();
        }
        static unsafe void TestSize()
        {
            //A :8,B :12,C :8,D :2
            Console.WriteLine($"A :{sizeof(A)},B :{sizeof(B)},C :{sizeof(C)},D :{sizeof(D)}");

        }

    }
}

ref: C#中sizeof的用法
ref: C#sizeof用法
详细参考:C++ struct union数据对齐