using System; using System.Collections; public class SimpleCollection : IEnumerable { public SimpleCollection(object[] array) { items = array; } public IEnumerator GetEnumerator() { return new Enumerator(this); } private class Enumerator : IEnumerator { public Enumerator(SimpleCollection obj) { oThis = obj; cursor = -1; } public bool MoveNext() { ++cursor; if (cursor > (oThis.items.Length - 1)) { return false; } return true; } public void Reset() { cursor = -1; } public object Current { get { if (cursor > (oThis.items.Length - 1)) { throw new InvalidOperationException( "Enumeration already finished"); } if (cursor == -1) { throw new InvalidOperationException( "Enumeration not started"); } return oThis.items[cursor]; } } private int cursor; private SimpleCollection oThis; } private object[] items = null; }
ASP.NET & Csharp (C#)
ASP.NET & Csharp (C#) , Here you can find my posts about .NET c# .
yield IEnumerator
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
public class Primes {
private long min;
private long max;
public Primes(long minimum, long maximum) {
min = minimum;
max = maximum;
}
public IEnumerator GetEnumerator() {
for (long possiblePrime = min; possiblePrime <= max; possiblePrime++) {
bool isPrime = true;
for (long possibleFactor = 2; possibleFactor <= (long)Math.Floor(Math.Sqrt(possiblePrime)); possibleFactor++) {
long remainderAfterDivision = possiblePrime % possibleFactor;
if (remainderAfterDivision == 0) {
isPrime = false;
break;
}
}
if (isPrime) {
yield return possiblePrime;
}
}
}
}
class Program {
static void Main(string[] args) {
Primes primesFrom2To1000 = new Primes(2, 1000);
foreach (long i in primesFrom2To1000)
Console.Write("{0} ", i);
}
}
[/csharp]
iterates two collections simultaneously
using System;
using System.Collections.Generic;
public class Starter {
public static void Main() {
MyClass obj = new MyClass();
foreach (int item in obj) {
Console.Write(item);
}
}
}
public class MyClass {
private int[] list1 = new int[] { 0, 2, 4, 6, 8 };
private int[] list2 = new int[] { 1, 3, 5, 7, 9 };
public IEnumerator
for (int index = 0; index < 4; ++index) {
yield return list1[index];
yield return list2[index];
}
}
}
[/csharp]
Tree Enumerator
using System; using System.Collections.Generic; using System.Linq; using System.Text; public class Tree<TItem> : IEnumerable<TItem> where TItem : IComparable<TItem> { public Tree(TItem nodeValue) { this.NodeData = nodeValue; this.LeftTree = null; this.RightTree = null; } public void Insert(TItem newItem) { TItem currentNodeValue = this.NodeData; if (currentNodeValue.CompareTo(newItem) > 0) { if (this.LeftTree == null) { this.LeftTree = new Tree<TItem>(newItem); } else { this.LeftTree.Insert(newItem); } } else { if (this.RightTree == null) { this.RightTree = new Tree<TItem>(newItem); } else { this.RightTree.Insert(newItem); } } } public void WalkTree() { if (this.LeftTree != null) { this.LeftTree.WalkTree(); } Console.WriteLine(this.NodeData.ToString()); if (this.RightTree != null) { this.RightTree.WalkTree(); } } public TItem NodeData { get; set; } public Tree<TItem> LeftTree { get; set; } public Tree<TItem> RightTree { get; set; } IEnumerator<TItem> IEnumerable<TItem>.GetEnumerator() { return new TreeEnumerator<TItem>(this); } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw new NotImplementedException(); } } class TreeEnumerator<T> : IEnumerator<T> where T : IComparable<T> { public TreeEnumerator(Tree<T> data) { this.currentData = data; } private void populate(Queue<T> enumQueue, Tree<T> tree) { if (tree.LeftTree != null) { populate(enumQueue, tree.LeftTree); } enumQueue.Enqueue(tree.NodeData); if (tree.RightTree != null) { populate(enumQueue, tree.RightTree); } } private Tree<T> currentData = null; private T currentItem = default(T); private Queue<T> enumData = null; T IEnumerator<T>.Current { get { if (this.enumData == null) throw new InvalidOperationException("Use MoveNext before calling Current"); return this.currentItem; } } void IDisposable.Dispose() { // throw new NotImplementedException(); } object System.Collections.IEnumerator.Current { get { throw new NotImplementedException(); } } bool System.Collections.IEnumerator.MoveNext() { if (this.enumData == null) { this.enumData = new Queue<T>(); populate(this.enumData, this.currentData); } if (this.enumData.Count > 0) { this.currentItem = this.enumData.Dequeue(); return true; } return false; } void System.Collections.IEnumerator.Reset() { throw new NotImplementedException(); } } class Program { static void Main(string[] args) { Tree<int> tree1 = new Tree<int>(10); tree1.Insert(5); tree1.Insert(11); tree1.Insert(5); tree1.Insert(-12); tree1.Insert(15); tree1.Insert(0); tree1.Insert(14); tree1.Insert(-8); tree1.Insert(10); foreach (int item in tree1) Console.WriteLine(item); } }
Enumerator Example (Versioned Collection)
using System; using System.Collections; public class Starter { public static void Main() { MyCollection simple = new MyCollection(new object[] { 1, 2, 3, 4, 5, 6, 7 }); IEnumerator enumerator = simple.GetEnumerator(); enumerator.MoveNext(); Console.WriteLine(enumerator.Current); enumerator.MoveNext(); simple[4] = 10; Console.WriteLine(enumerator.Current); enumerator.MoveNext(); } } public class MyCollection : IEnumerable { public MyCollection(object[] array) { items = array; version = 1; } public object this[int index] { get { return items[index]; } set { ++version; items[index] = value; } } public IEnumerator GetEnumerator() { return new Enumerator(this); } private class Enumerator : IEnumerator { public Enumerator(MyCollection obj) { oThis = obj; cursor = -1; version = oThis.version; } public bool MoveNext() { ++cursor; if (cursor > (oThis.items.Length - 1)) { return false; } return true; } public void Reset() { cursor = -1; } public object Current { get { if (oThis.version != version) { throw new InvalidOperationException("Collection was modified"); } if (cursor > (oThis.items.Length - 1)) { throw new InvalidOperationException("Enumeration already finished"); } if (cursor == -1) { throw new InvalidOperationException("Enumeration not started"); } return oThis.items[cursor]; } } private int version; private int cursor; private MyCollection oThis; } private object[] items = null; private int version; }
IEnumerable with a foreach loop
using System; using System.Collections.Generic; using System.Linq; public class MainClass { public static void Main() { IEnumerable<char> query = "Not what you might expect"; foreach (char vowel in "aeiou") query = query.Where(c => c != vowel); foreach (char c in query) Console.Write(c); } }
Extends IEnumerable
using System; using System.Collections.Generic; using System.Text; using System.Collections; public class Employee { public int currAge; public string fName, lName; public Employee() { } public Employee(string firstName, string lastName, int age) { currAge = age; fName = firstName; lName = lastName; } public override string ToString() { return string.Format("{0}, {1} is {2} years old", lName, fName, currAge); } } public class PeopleCollection : IEnumerable { private ArrayList arPeople = new ArrayList(); public PeopleCollection() { } public Employee GetEmployee(int pos) { return (Employee)arPeople[pos]; } public void AddEmployee(Employee p) { arPeople.Add(p); } public void ClearPeople() { arPeople.Clear(); } public int Count { get { return arPeople.Count; } } IEnumerator IEnumerable.GetEnumerator() { return arPeople.GetEnumerator(); } } class Program { static void Main(string[] args) { PeopleCollection myPeople = new PeopleCollection(); myPeople.AddEmployee(new Employee("Homer", "Simpson", 40)); myPeople.AddEmployee(new Employee("Marge", "Simpson", 38)); myPeople.AddEmployee(new Employee("Lisa", "Simpson", 9)); myPeople.AddEmployee(new Employee("Bart", "Simpson", 7)); myPeople.AddEmployee(new Employee("Maggie", "Simpson", 2)); foreach (Employee p in myPeople) Console.WriteLine(p); } }