Delegates And Events 2
/*
Learning C#
by Jesse Liberty
Publisher: O'Reilly
ISBN: 0596003765
*/
using System;
namespace DelegatesAndEvents
{
public enum comparison
{
theFirstComesFirst = 1,
theSecondComesFirst = 2
}
// A simple collection to hold two items.
class Pair
{
// Private array to hold the two objects.
private object[] thePair = new object[2];
// The delegate declaration.
public delegate comparison
WhichIsFirst(object obj1, object obj2);
// Passed in constructor takes two objects,
// added in order received.
public Pair(
object firstObject,
object secondObject)
{
thePair[0] = firstObject;
thePair[1] = secondObject;
}
// Public method that orders
// the two objects by whatever criteria the objects like!
public void Sort(
WhichIsFirst theDelegatedFunc)
{
if (theDelegatedFunc(thePair[0],thePair[1])
== comparison.theSecondComesFirst)
{
object temp = thePair[0];
thePair[0] = thePair[1];
thePair[1] = temp;
}
}
// Public method that orders
// the two objects by the reverse of whatever criteria
// the objects like!
public void ReverseSort(
WhichIsFirst theDelegatedFunc)
{
if (theDelegatedFunc(thePair[0],thePair[1]) ==
comparison.theFirstComesFirst)
{
object temp = thePair[0];
thePair[0] = thePair[1];
thePair[1] = temp;
}
}
// Ask the two objects to give their string value.
public override string ToString()
{
return thePair[0].ToString() + ", "
+ thePair[1].ToString();
}
}
class Dog
{
private int weight;
// A static delegate.
public static readonly Pair.WhichIsFirst OrderDogs =
new Pair.WhichIsFirst(Dog. WhichDogComesFirst);
public Dog(int weight)
{
this.weight=weight;
}
// Dogs are sorted by weight.
public static comparison WhichDogComesFirst(
Object o1, Object o2)
{
Dog d1 = (Dog) o1;
Dog d2 = (Dog) o2;
return d1.weight > d2.weight ?
comparison.theSecondComesFirst :
comparison.theFirstComesFirst;
}
public override string ToString()
{
return weight.ToString();
}
}
class Student
{
private string name;
// A static delegate.
public static readonly Pair.WhichIsFirst OrderStudents =
new Pair.WhichIsFirst(Student.WhichStudentComesFirst);
public Student(string name)
{
this.name = name;
}
// Students are sorted alphabetically.
public static comparison
WhichStudentComesFirst(Object o1, Object o2)
{
Student s1 = (Student) o1;
Student s2 = (Student) o2;
return (String.Compare(s1.name, s2.name) < 0 ?
comparison.theFirstComesFirst :
comparison.theSecondComesFirst);
}
public override string ToString()
{
return name;
}
}
public class TesterDelegatesAndEvents1
{
public void Run()
{
// Create two students and two dogs
// and add them to Pair objects.
Student Jesse = new Student("Jesse");
Student Stacey = new Student ("Stacey");
Dog Milo = new Dog(65);
Dog Fred = new Dog(12);
// Create the Pair object.
Pair studentPair = new Pair(Jesse,Stacey);
Pair dogPair = new Pair(Milo, Fred);
Console.WriteLine("studentPair\t\t\t: {0}",
studentPair.ToString());
Console.WriteLine("dogPair\t\t\t\t: {0}",
dogPair.ToString());
// Tell the student Pair to sort itself,
// passing in the Student delegate.
studentPair.Sort(Student.OrderStudents);
Console.WriteLine("After Sort studentPair\t\t: {0}",
studentPair.ToString());
studentPair.ReverseSort(Student.OrderStudents);
Console.WriteLine("After ReverseSort studentPair\t: {0}",
studentPair.ToString());
// Tell the Dog pair to sort itself,
// passing in the Dog delegate.
dogPair.Sort(Dog.OrderDogs);
Console.WriteLine("After Sort dogPair\t\t: {0}",
dogPair.ToString());
dogPair.ReverseSort(Dog.OrderDogs);
Console.WriteLine("After ReverseSort dogPair\t: {0}",
dogPair.ToString());
}
[STAThread]
static void Main()
{
TesterDelegatesAndEvents1 t = new TesterDelegatesAndEvents1();
t.Run();
}
}
}
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