Chapter review

For review, the complete version of the Default.aspx.cs file for this chapter, including comments, is shown in the following code block:

//using is a directive
//System is a name space
//name space is a collection of features that our needs to run
using System;
using System.Collections.Generic;
//public means accessible anywhere
//partial means this class is split over multiple files
//class is a keyword and think of it as the outermost level of grouping
//:System.Web.UI.Page means our page inherits the features of a Page
public partial class _Default : System.Web.UI.Page
{
    protected void Button1_Click(object sender, EventArgs e)
    {
        sampLabel.Text = "";//clear label every time
        Quad sqr = new Square("John",4);//make a square
        Quad rect = new Rectangle("Bob", 2, 5);//make a rectangle
        Quad rect2 = new Rectangle("Jerry", 4, 5);//make another rectangle
        //stick all these shapes into a list of quads
        List<Quad> lst = new List<Quad>(new Quad[] { sqr, rect,rect2});
        lst.Sort();//sort the list
        if(lst[0] </span>is Square) //if it's asquare
 {
 //down cast to a square, and call Perimeter on it
 sampLabel.Text += ((Square)lst[0]).Perimeter();
 }
 else if(lst[0] is Rectangle)
 {
 //if it's a rectangle, down cost to a rectangle, 
 //and call Perimeter
 sampLabel.Text += ((Rectangle)lst[0]).Perimeter();
 }
 }
}