What processes and consequences occur when an object is passed to a function or method in programming?

In C#, when passing an object to a function or method, a copy of the reference to that object is passed, not the object itself. This means that inside the method, you can modify the state of the object (its fields and properties), and these changes will be visible outside the method because the reference points to the same object in memory.

However, if you assign a new reference to the parameter inside the method (e.g., param = new Object()), it will not affect the original reference outside the method, as the copy of the reference is changed locally.

Example:

class Person {
    public string Name;
}

void ChangeName(Person p) {
    p.Name = "Ivan"; // will change the object's name
    p = new Person(); // will only change local reference, not outside
    p.Name = "Peter";
}

Person person = new Person { Name = "Alexey" };
ChangeName(person);
Console.WriteLine(person.Name); // Outputs "Ivan"

Thus, passing an object is passing a reference by value. Changes to the object's state are preserved, but reassigning the reference does not affect the original.