Basics

Value Types

int, float, long, char, bool, byte, decimal, double, enum, sbyte, short, struct, uint, ulong, ushort

Use Stack memory 

Reference Types

A type that is defined as a string, class, record, delegate, array, or interface

Heap ?

public string ShapreToStrin(object) => shape switch {

Circle => "Circle",

Square => "Square",

_ => "Unknown"

 };