Writing the Main function code

That's that for our class definitions. Let's move on and get into the body of Main to create our main program. Type the following within the Main method:

Shape shape = new Rectangle(4, 5); 

On the left-hand side, we have Shape because both Circle and Rectangle derive from Shape. We don't have any code in the Shape class to define shapes. We are using it simply so that we can write Shape on the left-hand side to create new objects from that parent class. We're creating a rectangle, so we need to define the dimensions as 4 by 5.

Next, we come to the subject of this chapter: our switch block. On the next line, type the following:

switch(shape) 
{ 
 
} 

This is a new feature of C# 7.0. It is possible to switch between different data types, such as Shape, for example. Inside the curly braces of the switch block, type the following:

case Rectangle r when (r.Width == r.Height): 

We're doing some really simple math here to check whether a rectangle is actually a square. We...