Better Understanding of State Management in ASP.Net

For some time I've been using all of these special ASP.Net objects to assist with state management:

• Cache
• Application
• Session

Up until now though, I was misinformed about something. I had thought that when I retrieved a complex object out of one of these state management objects that I was getting a copy of it. In this way, I could do some work on the "temporary object" but then had to save it back in order for the change to be permanent.

This is absolutely incorrect!

So, for example:

DataTable dtEmployees = (DataTable)Session["Employees"];
DataRow row = dtEmployees.Rows[5];
row["FirstName"] = "Steve";

I do NOT have to use the following line:

Session["Employees"] = dtEmployees;

Rather, right after the name was changed above, I could have done this:

((DataTable)Session["Employees"]).Rows[5]["FirstName"]

and "Steve" would be returned!