using statement with IDisposable interface

   
 
using System;

public class MyValueReport {
    int InstanceNumber;
    public MyValueReport(int InstanceNumber) {
        this.InstanceNumber = InstanceNumber;
        Console.WriteLine(InstanceNumber);
    }
}

public class MyValue : IDisposable {
    int n;
    public MyValue(int n) {
        this.n = n;
        MyValueReport MyReport = new MyValueReport(n);
    }

    public void Dispose() {
        MyValueReport MyReport = new MyValueReport(this.n);
        GC.SuppressFinalize(this); 
    }
    ~MyValue() {
        MyValueReport MyReport = new MyValueReport(this.n);
    }
}

public class Test {
    static void Main() {
        MyValue d1 = new MyValue(1);
        MyValue d2 = new MyValue(2);
        MyValue d3 = new MyValue(3);
        d1 = null;
        using (d3) {
            MyValue d4 = new MyValue(4);
        }
        d2.Dispose();

    }
}

    


The constructor initializes the internal object. The Dispose method closes the file resource. The destructor delegates to the Dispose method.

   
 

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(&#039; &#039;);
            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);
        }
   }
}