Session object changes when object is updated

Questions

I have this really weird problem and I'm sure I'm missing something obvious here. I have these two lines:.

HttpContext.Current.Session[listModelType + "ListModel"] = listModel; listModel.ProductRows = new Collection<ProductRow>(listModel.ProductRows.Where(r => r.ParentRowId == 0).ToList());

After the second line is executed my session object is updated as well (according to "Watch" in Visual Studio)

What am I missing here?

I have tried

int i = 0; HttpContext.Current.Session["i"] = i; i++;

and HttpContext.Current.Session["i"] remains 0.

Answers

n your first example you are storing a reference to the object (The lists memory location). So if the list is updated it will reflect in the session. This is a reference type.
In the second example you are using a value type:

int i = 0; HttpContext.Current.Session["i"] = i; i++;

You declare i and set it to 0 (Value type)
You store the value 0 in the session. (Not the memory location of i)
You increment i but the session still has the value 0