C # difference of struct class in Marshal. sizeof

Difference between struct and class

The most important thing is the difference between value and object.

However, it is very important to find another interesting phenomenon recently.

In a project, struct is used because of various structures. However, it is a little troublesome. Passing values consumes a lot and does not like REF (because I like to write generic functions)

So we adopted the class, and then we went smoothly .....

[Serializable] // indicates serializable [structlayout (layoutkind. sequential, charset = charset. ANSI, pack = 1)] // tiled structure; ANSI characters; each structure member is aligned by 1 byte [rdmsgid (rdmsgid. e_fid_mc_marketinfo)] class marketinfo {[financialas (unmanagedtype. byvalarray, sizeconst = 5)] public marketdatatick [] marketdataticks ;}

It should be said that marshal. sizeof (marketinfo) is equal to sizeof (marketdatatick) * 5

But actually: 4*5 = 20

Why? Because the structure of marketdatatick is set to class, it is easy to change it to struct!

Tragedy!