C# / .NET Junior (0–2 yrs) Concepts Very frequent C# memory types fundamentals

What is the difference between value types and reference types in C#?

cs-jun-001

Your answer

Answer as you would in a real interview — explain your thinking, not just the conclusion.

Model answer

Value types — structs, primitives like int and bool, and enums — store their data directly on the stack or inline within a containing object. Assignment creates an independent copy, so changing one variable does not affect the other. Reference types — classes, interfaces, delegates, arrays — store a pointer to heap-allocated memory. Assignment copies the reference, meaning two variables can point to the same object. Modifying the object through one variable is visible through the other. Null assignment is only valid for reference types unless you use Nullable<T> (int?).

Code example

int a = 10;
int b = a;   // copy of value
b = 20;
Console.WriteLine(a); // 10 — unaffected

var list1 = new List<int> { 1, 2, 3 };
var list2 = list1;   // copy of reference
list2.Add(4);
Console.WriteLine(list1.Count); // 4 — same object

Follow-up

When would you choose a struct over a class? What is the general guideline for struct size in .NET?