What is the difference between value-passed data types and reference-passed data types?

In C#, data types are divided into value types and reference types, and this affects how data is passed:

• Pass by value:

  • The actual value is copied.
  • Changes inside the method do not affect the original.
  • Examples: int, double, struct.

• Pass by reference:

  • A reference to the object in memory is copied.
  • Changes inside the method reflect on the original object.
  • Examples: class, string (although strings are immutable), arrays.

Example:

void ModifyValue(int x) {
    x = 10; // only the local copy will change
}

void ModifyReference(Person p) {
    p.Name = "Ivan"; // the object referenced by p will change
}

int a = 5;
ModifyValue(a);
Console.WriteLine(a); // 5

Person person = new Person { Name = "Peter" };
ModifyReference(person);
Console.WriteLine(person.Name); // Ivan

Thus, understanding the difference is important for managing data state and preventing unexpected changes.