using System;
using System.Collections;

namespace Levensoft
{
    // data object contained in PeopleCollection
    public class Person
    {
        public Person(string name, int age)
        {
            this.name = name;
            this.age = age;
        }
        
        public string Name
        {
            get { return name; }
        }
        public int Age
        {
            get { return age; }
        }

        private string name;
        private int age;
    }

    public class PeopleCollection : IEnumerable
    {
        // IEnumerable
        public IEnumerator GetEnumerator()
        {
            return new PeopleCollectionEnum(_peopleCollection);
        }

        // IEnumerator
        private class PeopleCollectionEnum : IEnumerator
        {
            private Person[] _peopleCollection;
            private int _position = -1;

            public PeopleCollectionEnum(Person[] list)
            {
                _peopleCollection = list;
            }

            public bool MoveNext()
            {
                _position++;

                return (_position < _peopleCollection.Length);
            }
            public void Reset()
            {
                _position = -1;
            }
            public object Current
            {
                get
                {
                    try
                    {
                        return _peopleCollection[_position];
                    }
                    catch (IndexOutOfRangeException)
                    {
                        throw new InvalidOperationException();
                    }
                }
            }
        }

        public PeopleCollection()
        {
            _peopleCollection = new Person[3]
            {
                new Person("Bob", 30),
                new Person("Jim", 31),
                new Person("Sue", 29),
            };
        }

        // Indexer & Length provide the ability of Array-like accessor
        public Person this[int index]
        {
            get
            {
                try
                {
                    return _peopleCollection[index];
                }
                catch (IndexOutOfRangeException) { throw; }
            }
        }

        public int Length
        {
            get
            {
                return _peopleCollection.Length;
            }
        }

        private Person[] _peopleCollection;
    }

    public class test
    {
        public static void Main()
        {
            PeopleCollection peopleCollection = new PeopleCollection();

            // IEnumerable & IEnumerator enable foreach statement
            foreach (Person p in peopleCollection)
            {
                Console.WriteLine(p.Name + "\t\t" + p.Age);
            }

            // Indexer & Length enable for statement
            for (int i = 0; i < peopleCollection.Length; i++)
            {
                Console.WriteLine(peopleCollection[i].Name + "\t\t" + peopleCollection[i].Age);
            }
        }
    }
}

例二：Collection & Iterator在C# 2.0中的实现

using System;
using System.Collections;

namespace Levensoft
{
    public class Person
    {
        public Person(string name, int age)
        {
            this.name = name;
            this.age = age;
        }
        
        public string Name
        {
            get { return name; }
        }
        public int Age
        {
            get { return age; }
        }

        private string name;
        private int age;
    }

    public class PeopleCollection : IEnumerable
    {
        public IEnumerator GetEnumerator()
        {
            // iterator block
            for (int i = 0; i < _peopleCollection.Length; i++)
            {
                yield return _peopleCollection[i];
            }
        }

        public PeopleCollection()
        {
            _peopleCollection = new Person[3]
            {
                new Person("Bob", 30),
                new Person("Jim", 31),
                new Person("Sue", 29),
            };
        }

        public Person this[int index]
        {
            get
            {
                try
                {
                    return _peopleCollection[index];
                }
                catch (IndexOutOfRangeException) { throw; }
            }
        }

        public int Length
        {
            get
            {
                return _peopleCollection.Length;
            }
        }

        private Person[] _peopleCollection;
    }

    public class test
    {
        public static void Main()
        {
            PeopleCollection peopleCollection = new PeopleCollection();

            foreach (Person p in peopleCollection)
            {
                Console.WriteLine(p.Name + "\t\t" + p.Age);
            }

            for (int i = 0; i < peopleCollection.Length; i++)
            {
                Console.WriteLine(peopleCollection[i].Name + "\t\t" + peopleCollection[i].Age);
            }
        }
    }
}

从例二可以看出，C# 2.0通过iterator block大大简化了Collection的遍历机制（iterator）。实际上，iterator block是C# 2.0为程序员提供的一种便利设施（handy facility），C#编译器在编译时，仍然生成如例一所示的enumerator class。

• InstallUtil.InstallLog
  该文件含有安装过程的描述。
• assemblyname.InstallLog
  该文件含有安装过程的Commit阶段的信息。
• assemblyname.InstallState
  该文件含有卸载时需要的信息。注意：卸载应用程序时，当前目录必须含有该文件，否则卸载失败。

由此简单说明可以看出，.NET Framework通过InstallUtil.exe/Installer Components对服务器端应用程序提供了一个框架性的安装工具，方便了Windows Service这类服务器端应用程序的开发。

下面的例子演示了Installer Class的用法：

using System;
using System.Collections;
using System.ComponentModel;
using System.Configuration.Install;

namespace InstallerDemo
{
    // RunInstallerAttribute declares MyInstaller class is an installer component.
    [RunInstaller(true)]
    public class MyInstaller : Installer
    {
        public MyInstaller() : base()
        {
            // Attach the 'BeforeInstall' event
            this.BeforeInstall += MyInstallerBeforeInstall;

            // Attach the 'AfterInstall' event
            this.AfterInstall += MyInstallerAfterInstall;

            // Attach the 'Committed' event
            this.Committed += MyInstallerCommitted;

            // Attach the 'Committing' event
            this.Committing += MyInstallerCommitting;
        }

        // Event handler for 'BeforeInstall'
        private void MyInstallerBeforeInstall(object sender, InstallEventArgs args)
        {
            Console.WriteLine("Before install...");
        }

        // Event handler for 'AfterInstall'
        private void MyInstallerAfterInstall(object sender, InstallEventArgs args)
        {
            Console.WriteLine("After install.");
        }

        // Event handler for 'Committed'
        private void MyInstallerCommitted(object sender, InstallEventArgs args)
        {
            Console.WriteLine("Installer committed.");
        }
        // Event handler for 'Committing'
        private void MyInstallerCommitting(object sender, InstallEventArgs args)
        {
            Console.WriteLine("Installer committing...");
        }

        // Override the 'Install' method
        public override void Install(IDictionary savedState)
        {
            base.Install(savedState);
            Console.WriteLine("Installing...");
        }

        // Override the 'Commit' method
        public override void Commit(IDictionary savedState)
        {
            base.Commit(savedState);
            Console.WriteLine("Committing...");
        }

        // Override the 'Rollback' method
        public override void Rollback(IDictionary savedState)
        {
            base.Rollback(savedState);
            Console.WriteLine("Rolling back...");
        }

        public static void Main()
        {
            // ......
        }
    }
}

例子中注册事件处理的代码利用了C#的简化语法：

this.BeforeInstall += MyInstallerBeforeInstall;

完整的语法应该是：

this.BeforeInstall += new InstallEventHandler(MyInstallerBeforeInstall);

由此可见，C# syntactical sugar为开发人员（特别是熟悉C/C++的开发人员）提供了莫大的便利，使得代码更加自然与直观。

上述的InstallEventHandler的声明是：

public delegate void InstallEventHandler(Object sender, InstallEventArgs args);

根据此delegate的声明，可知MyInstallerBeforeInstall的声明必须是：

void MyInstallerBeforeInstall(Object sender, InstallEventArgs args);