Objects between postbacks

Hello,

Help me please with something that I think is very basic...

1. Suppose I have a class called MyClass. It is placed in App_Code folder of my web-application:

public class MyClass
{
private IView view;
private DateTime time;

public MyClass(IView view)
{
this.view = view;
}

public DateTime Time
{
get { return time; }
set { time = value; }
}

// Here comes some other code...
}

2. Now, I have an ASPX page called MyPage.aspx. It implements the IView, it has a private member of type MyClass, and here are some relevant methods:

public partial class MyPage: System.Web.UI.Page, IView
{
private MyClass myClass;

// CTOR
public MyPage()
{
myClass = new MyClass(this);
}

protected Page_Load(object sender, EventArgs e)
{
if (!IsPostBack) { myClass.Time = DateTime.Now; }
}

protected MyButton_Click(object sender, EventArgs e)
{
lblTime = myClass.Time;
}

// Here comes some other code
}

Ok. What I am expecting is:
- MyPage CTOR creates an object of type MyClass;
- Then Page_Load sets the current time;
- Then the user clicks MyButton and the stored time is displayed in MyLabel.

So actually I expect that the MyClass object will be stored in the current session and behave like it would behave in usual non-Web application.

But... I get something strange. First of all, the "time" member of myClass is NOT stored. Well, I know about this kind of problems, so I know that I should probably use Session[] to store the values. But the strange thing is that the "view" member IS stored! I can see that using the debugger...

So please explain me, when the variables ARE stored between postbacks and when they ARE NOT... Thank you!