Classes are reference types. That means that when we create a new instance of a class and store it in a variable, the variable is a reference to the object.

Let’s see what’s happening behind the scenes. When this code is run:

Dissertation diss1 = new Dissertation();

A new Dissertation instance is constructed and stored in the computer’s memory. You can imagine a slot in your computer holding the instance’s type, property values, etc. diss1 is a reference to that location in memory.

diss1 is not the actual object, it is a reference to the object. Thus an object can have multiple references:

Dissertation diss1 = new Dissertation();
Dissertation diss2 = diss1;

Now there are two references to the same location in memory: we can say that diss1 and diss2 refer to the same object. If changes are made to that object, then they will be reflected in both references to it:

Dissertation diss1 = new Dissertation();
Dissertation diss2 = diss1;
diss1.CurrentPage = 0;
diss2.CurrentPage = 16;
Console.WriteLine(diss1.CurrentPage);
Console.WriteLine(diss2.CurrentPage);

• The middle two lines of this code are setting the CurrentPage property of the same object (first setting it to 0, then 16)
• The last two lines will print the same value, 16

You can imagine references like directions to a house: they tell you where to find the house, but they are not the house itself!