using System;
using System.IO;
public class WriteToFile : IDisposable {
public WriteToFile(string _file, string _text) {
file = new StreamWriter(_file, true);
text = _text;
}
public void WriteText() {
file.WriteLine(text);
}
public void Dispose() {
file.Close();
}
~WriteToFile() {
Dispose();
}
private StreamWriter file;
private string text;
}
public class Writer {
public static void Main() {
WriteToFile sample = new WriteToFile("sample.txt", "My text file");
sample.WriteText();
sample.Dispose();
}
}
Protecting Against Double Disposal
using System;
public class MyClass : IDisposable
{
private string name;
public MyClass(string name) { this.name = name; }
override public string ToString() { return name; }
~MyClass()
{
Dispose();
Console.WriteLine("~MyClass()");
}
private bool AlreadyDisposed = false;
public void Dispose()
{
if (!AlreadyDisposed)
{
AlreadyDisposed = true;
Console.WriteLine("Dispose()");
GC.SuppressFinalize(this);
}
}
}
public class MainClass
{
public static void Main(string[] args)
{
MyClass t = new MyClass("Foo");
Console.WriteLine(t);
t.Dispose();
t.Dispose();
GC.Collect();
GC.WaitForPendingFinalizers();
}
}
Derived Disposable Classes
using System;
public class MyClass : IDisposable
{
protected string name;
public MyClass(string name) { this.name = name; }
override public string ToString() { return name; }
~MyClass() { Dispose(); Console.WriteLine("~MyClass()"); }
public void Dispose()
{
Console.WriteLine("MyClass.Dispose()");
GC.SuppressFinalize(this);
}
}
public class SonOfMyClass : MyClass, IDisposable
{
public SonOfMyClass(string name) : base(name) { }
override public string ToString() {
return name;
}
~SonOfMyClass() {
Dispose();
Console.WriteLine("~SonOfMyClass()");
}
new public void Dispose()
{
base.Dispose();
GC.SuppressFinalize(this);
}
}
class DerivedDisposeApp
{
static void Main(string[] args)
{
DoSomething();
}
static void DoSomething()
{
SonOfMyClass s = new SonOfMyClass("Bar");
Console.WriteLine(s);
s.Dispose();
}
}
The IDisposable Interface
using System;
public class MyClass : IDisposable
{
private string name;
public MyClass(string name) { this.name = name; }
override public string ToString() { return name; }
~MyClass()
{
Dispose();
Console.WriteLine(“~MyClass(): ” +name);
}
public void Dispose()
{
Console.WriteLine(“Dispose(): ” +name);
GC.SuppressFinalize(this);
}
}
public class DisposableApp
{
public static void Main(string[] args)
{
Console.WriteLine(“start of Main, heap used: {0}”, GC.GetTotalMemory(true));
DoSomething();
Console.WriteLine(“end of Main, heap used: {0}”, GC.GetTotalMemory(true));
}
public static void DoSomething()
{
MyClass[] ta = new MyClass[3];
for (int i = 0; i < 3; i++) { ta[i] = new MyClass(String.Format("object #" +i)); Console.WriteLine("Allocated {0} objects, heap used: {1}", i+1, GC.GetTotalMemory(true)); } for (int i = 0; i < 3; i++) { ta[i].Dispose(); ta[i] = null; GC.Collect(); GC.WaitForPendingFinalizers(); Console.WriteLine("Disposed {0} objects, heap used: {1}",i+1, GC.GetTotalMemory(true)); } } } [/csharp]
Implements ICustomFormatter
using System;
using System.Text;
using System.Globalization;
public class WordyFormatProvider : IFormatProvider, ICustomFormatter {
static readonly string[] _numberWords = "zero one two three four five six seven eight nine minus point".Split();
IFormatProvider _parent; // Allows consumers to chain format providers
public WordyFormatProvider() : this(CultureInfo.CurrentCulture) { }
public WordyFormatProvider(IFormatProvider parent) {
_parent = parent;
}
public object GetFormat(Type formatType) {
if (formatType == typeof(ICustomFormatter)) return this;
return null;
}
public string Format(string format, object arg, IFormatProvider prov) {
if (arg == null || format != "W")
return string.Format(_parent, "{0:" + format + "}", arg);
StringBuilder result = new StringBuilder();
string digitList = string.Format(CultureInfo.InvariantCulture,
"{0}", arg);
foreach (char digit in digitList) {
int i = "0123456789-.".IndexOf(digit);
if (i == -1) continue;
if (result.Length > 0) result.Append(' ');
result.Append(_numberWords[i]);
}
return result.ToString();
}
}
public class MainClass {
public static void Main() {
double n = -123.45;
IFormatProvider fp = new WordyFormatProvider();
Console.WriteLine(string.Format(fp, "{0:C} in words is {0:W}", n));
}
}
Gets the hash code for an object using a comparer. Correctly handles null.
//******************************
// Written by Peter Golde
// Copyright (c) 2004-2007, Wintellect
//
// Use and restribution of this code is subject to the license agreement
// contained in the file "License.txt" accompanying this file.
//******************************
using System;
using System.Collections;
using System.Collections.Generic;
namespace Wintellect.PowerCollections
{
/// <summary>
/// A holder class for various internal utility functions that need to be shared.
/// </summary>
internal static class Util
{
/// <summary>
/// Gets the hash code for an object using a comparer. Correctly handles
/// null.
/// </summary>
/// <param name="item">Item to get hash code for. Can be null.</param>
/// <param name="equalityComparer">The comparer to use.</param>
/// <returns>The hash code for the item.</returns>
public static int GetHashCode<T>(T item, IEqualityComparer<T> equalityComparer)
{
if (item == null)
return 0x1786E23C;
else
return equalityComparer.GetHashCode(item);
}
}
}
Implement IComparer
using System;
using System.Collections;
class Album : IComparable, ICloneable {
private string _Title;
private string _Artist;
public Album(string artist, string title) {
_Artist = artist;
_Title = title;
}
public string Title {
get {
return _Title;
}
set {
_Title = value;
}
}
public string Artist {
get {
return _Artist;
}
set {
_Artist = value;
}
}
public override string ToString() {
return _Artist + ", " + _Title;
}
public int CompareTo(object o) {
Album other = o as Album;
if (other == null)
throw new ArgumentException();
if (_Artist != other._Artist)
return _Artist.CompareTo(other._Artist);
else
return _Title.CompareTo(other._Title);
}
public object Clone() {
return new Album(_Artist, _Title);
}
}
class TitleComparer : IComparer {
public int Compare(object l, object r) {
Album left = l as Album;
Album right = r as Album;
if ((left == null) || (right == null))
throw new ArgumentException();
if (left.Title != right.Title)
return left.Title.CompareTo(right.Title);
else
return left.Artist.CompareTo(right.Artist);
}
}
class Class1 {
static void Main(string[] args) {
ArrayList arr = new ArrayList();
arr.Add(new Album("G", "A"));
arr.Add(new Album("B", "G"));
arr.Add(new Album("S", "A"));
arr.Sort();
try {
foreach (Album a in arr) {
Console.WriteLine(a);
}
} catch (System.InvalidCastException e) {
}
arr.Sort(new TitleComparer());
foreach (Album a in arr) {
Console.WriteLine(a);
}
Album l = new Album("L", "G");
arr.Sort();
int index = arr.BinarySearch(l);
Console.WriteLine(index.ToString());
arr.Sort(new TitleComparer());
index = arr.BinarySearch(l, new TitleComparer());
Console.WriteLine(index.ToString());
}
}

