Question

I have the following code:

public class Test {     public static void Main()     {         List<Person> list = new List<Person>();         Person person = new Person() { Name='Chris' };         list.Add(person);          person = new Person(){ Name='Wilson the cat' };         list.Add(person);          Console.WriteLine(list[0].Name);         Console.WriteLine(list[1].Name);         Console.ReadLine();     } }  public class Person {     public string Name {get;set;}    } 

My question is where does the first person instance go? Does the CLR magically create a new instance of it somewhere? Is there anyway of referencing it outside of the list – e.g. where does it go after the method has completed? What method is used for storing objects in a collection (that was 4 questions).

Answer 1

    List<Person> list = new List<Person>();      Person person = new Person() { Name='Chris' };     // your person object lives on the heap. The person variable is just     // a pointer of that object on the heap. Note that the pointer lives     // on the stack, and the object it points to lives on the heap.      list.Add(person);     // when you add your person to to the list, all it does it pass a     // copy of the *pointer* to the list's method. List has access to this     // object through the pointer.      person = new Person(){ Name='Wilson the cat' };     // new'ing up a instance of person creates another person object on     // the heap. Note that this doesn't overwrite our original person created above,     // because our original person sits in an entirely differently memory      // location.      // We did, however overwrite our pointer variable by assigning it a new     // location to point at. This doesn't affect the object we put into our     // list since the list received a copy of our original pointer :)      list.Add(person);      Console.WriteLine(list[0].Name);     // list[0] has a pointer to the first object we created       Console.WriteLine(list[1].Name);     // list[1] has a pointer to the second object we created.      Console.ReadLine();      // when this methods goes out of scope (i.e. when the stack frame is     // popped), the pointers will be dropped from memory, and the objects     // on the heap will no longer have any live references to them, so     // they'll be eaten by the garbage collector.