C＃类对象列表更改为匹配最后一个对象？

Question

I am trying to make an 'archive' of all past versions of a class (or struct, for that matter). But as a class is created to be added to the list, it seems the sum total of listed classes alter themselves to match.

My code goes along something like this:

public class State
{
  public int i;

  public State(int newI)
  {
    i = newI;
  }
}

List<State> list = new List<State>;

public void NewEntry(int x)
{
  State state = new State(x); //this is the line in question
  list.Add(state)
}

By the time the State constructor has executed, all states in list have been changed to match their i to the fresh value of x.

What am I missing, besides basic knowledge and understanding? :P

Answer 1

Uhm... Is not very clear from your example, but let me guess what the problem is.

When you add the class to the list, you may be adding a reference.

When you use:

State x = new State();
State b = x;

box "x" and "b" points to same object, xi and bi are the same memory.

IF and if State is a struct, then it's different

public **struct** State
{
  public int i;

  public State(int newI)
  {
    i = newI;
  }
}

Then

State x = new State();
State b = x;

will make a copy of every value field (like ints and doubles) and xi will be in a different memory location than bi

Is this related to your issue?