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Reference Fundamentals
References of the Same Type

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 refers to memory location

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;

diss1 and diss2 refer to the same memory location

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!

Instructions

1.

Create a new Diary object with a current page of 5 using the constructor new Diary(5). Store a reference to that object and name it dy1. Its type should also be Diary.

2.

Create another reference to that object and name it dy2.

3.

Flip dy2 by calling its Flip() method. This increases the CurrentPage property by 1.

4.

Print out the CurrentPage property for both dy1 and dy2. They should be the same!

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