return IEnumerable

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using System;
using System.Collections.Generic;

class IteratorDemo {
    static IEnumerable<int> OneTwoThree() {
        Console.WriteLine("Returning 1");
        yield return 1;
        Console.WriteLine("Returning 2");
        yield return 2;
        Console.WriteLine("Returning 3");
        yield return 3;
    }
    static void Main() {
        foreach (var number in OneTwoThree()) {
            Console.WriteLine(number);
        }
    }
}

    


yield return

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using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;

class Program {
    public static IEnumerable<string> SimpleList() {
        yield return "1";
        yield return "2";
        yield return "3";
    }

    public static void Main(string[] args) {
        foreach (String item in SimpleList())
            Console.WriteLine(item);

    }
}

    


The Dispose Pattern

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using System;


public class MyClass {
    private string name;
    public MyClass(string name) { this.name = name; }
    override public string ToString() { return name; }
    ~MyClass() { Console.WriteLine("~MyClass()"); }
    public void Dispose() {
        Console.WriteLine("Dispose()");
    }
}

public class GarbageDisposalApp {
    public static void Main(string[] args) {
        DoSomething();
        Console.WriteLine("end of Main");
    }
    public static void DoSomething() {
        MyClass t = new MyClass("Foo");
        Console.WriteLine(t);
        t.Dispose();
        t = null;
        GC.Collect();
        GC.WaitForPendingFinalizers();
    }
}

    


using statement with IDisposable interface

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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.

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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

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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

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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();
    }
}