Question

The ArrayList class can only contain references to objects but what happens when you store a value type such as integers?

string str = "Hello";
int i = 50;

ArrayList arraylist = new ArrayList();

arraylist.Add(str); // Makes perfectly sense: 
                    // Reference to string-object (instance) "Hello" is added to 
                    // index number 0

arraylist.Add(i);   // What happens here? How can a reference point to a value 
                    // type? Is the value type automatically converted to an 
                    // object and thereafter added to the ArrayList?

Answer 1

It’s called “boxing”: automagically the int is converted to a reference type. This does cost some performance.

See also Boxing and Unboxing.