// Copyright © Microsoft Corporation. All Rights Reserved. // This code released under the terms of the // MICROSOFT LIMITED PUBLIC LICENSE version 1.1 (MS-LPL, http://go.microsoft.com/?linkid=9791213.) // // Copyright (C) Microsoft Corporation. All rights reserved. using System; using System.Collections; using System.Collections.Generic; using System.Text; namespace Generics_CSharp { //Type parameter T in angle brackets. public class MyList<T> : IEnumerable<T> { protected Node head; protected Node current = null; // Nested type is also generic on T protected class Node { public Node next; //T as private member datatype. private T data; //T used in non-generic constructor. public Node(T t) { next = null; data = t; } public Node Next { get { return next; } set { next = value; } } //T as return type of property. public T Data { get { return data; } set { data = value; } } } public MyList() { head = null; } //T as method parameter type. public void AddHead(T t) { Node n = new Node(t); n.Next = head; head = n; } // Implement GetEnumerator to return IEnumerator<T> to enable // foreach iteration of our list. Note that in C# 2.0 // you are not required to implement Current and MoveNext. // The compiler will create a class that implements IEnumerator<T>. public IEnumerator<T> GetEnumerator() { Node current = head; while (current != null) { yield return current.Data; current = current.Next; } } // We must implement this method because // IEnumerable<T> inherits IEnumerable IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } } public class SortedList<T> : MyList<T> where T : IComparable<T> { // A simple, unoptimized sort algorithm that // orders list elements from lowest to highest: public void BubbleSort() { if (null == head || null == head.Next) return; bool swapped; do { Node previous = null; Node current = head; swapped = false; while (current.next != null) { // Because we need to call this method, the SortedList // class is constrained on IEnumerable<T> if (current.Data.CompareTo(current.next.Data) > 0) { Node tmp = current.next; current.next = current.next.next; tmp.next = current; if (previous == null) { head = tmp; } else { previous.next = tmp; } previous = tmp; swapped = true; } else { previous = current; current = current.next; } }// end while } while (swapped); } } // A simple class that implements IComparable<T> // using itself as the type argument. This is a // common design pattern in objects that are // stored in generic lists. public class Person : IComparable<Person> { string name; int age; public Person(string s, int i) { name = s; age = i; } // This will cause list elements // to be sorted on age values. public int CompareTo(Person p) { return age - p.age; } public override string ToString() { return name + ":" + age; } // Must implement Equals. public bool Equals(Person p) { return (this.age == p.age); } } class Generics { static void Main(string[] args) { //Declare and instantiate a new generic SortedList class. //Person is the type argument. SortedList<Person> list = new SortedList<Person>(); //Create name and age values to initialize Person objects. string[] names = new string[] { "Franscoise", "Bill", "Li", "Sandra", "Gunnar", "Alok", "Hiroyuki", "Maria", "Alessandro", "Raul" }; int[] ages = new int[] { 45, 19, 28, 23, 18, 9, 108, 72, 30, 35 }; //Populate the list. for (int x = 0; x < names.Length; x++) { list.AddHead(new Person(names[x], ages[x])); } Console.WriteLine("Unsorted List:"); //Print out unsorted list. foreach (Person p in list) { Console.WriteLine(p.ToString()); } //Sort the list. list.BubbleSort(); Console.WriteLine(String.Format("{0}Sorted List:", Environment.NewLine)); //Print out sorted list. foreach (Person p in list) { Console.WriteLine(p.ToString()); } Console.WriteLine("Done"); } } }