Question

In the code below ViewState["L"] stores a List<string>. I create a new instance of List and assign the casted value of a viewstate to it.

List<string> myList = new List<string>();

myList=(List<string>)ViewState["L"];

Response.Write(myList.Equals(ViewState["L"]));// returns True

As you can see, .Equals() method tells me that the Viewstate object and the List object are the same.
Now my question to you guys is how can a List and a Viewstate be a reference to the same object? What does the heap memory at that location actually hold?

Update
The code below demonstrates that any variable that gets assigned a cast value of the viewstate, are all pointing to the same object.

   List<string> myList1 = new List<string>();
    myList1.Add("apple");
    ViewState["L"] = myList1;

    List<string> myList2 = new List<string>();
    myList2 = (List<string>)ViewState["L"];

    List<string> myList3 = new List<string>();
    myList3 = (List<string>)ViewState["L"];;

    myList3.Add("orange");//Here myList2 gets an orange too !

I think, Thomas is right.

Answer 1

how can a List and a Viewstate be a reference to the same object?

It’s not “a ViewState”, but an element of the ViewState. ViewState["L"] returns an object which is actually a List<string> (the same one you just assigned to myList)