public class PooledObject
    {
        DateTime _createdAt = DateTime.Now;

        public DateTime CreatedAt
        {
            get { return _createdAt; }
        }

        public string TempData { get; set; }

        public void DoSomething(string name)
        {
            Console.WriteLine($"{name} : {TempData} is written on {CreatedAt}");
        }
    }

public static class Pool
{
    private static List<PooledObject> _available = new List<PooledObject>();
    private static List<PooledObject> _inUse = new List<PooledObject>();
 
    public static PooledObject GetObject()
    {
        lock(_available)
        {
            if (_available.Count != 0)
            {
                PooledObject po = _available[0];
                _inUse.Add(po);
                _available.RemoveAt(0);
                return po;
            }
            else
            {
                PooledObject po = new PooledObject();
                _inUse.Add(po);
                return po;
            }
        }
    }
 
    public static void ReleaseObject(PooledObject po)
    {
        CleanUp(po);
 
        lock (_available)
        {
            _available.Add(po);
            _inUse.Remove(po);
        }
    }
 
    private static void CleanUp(PooledObject po)
    {
        po.TempData = null;
    }
}

            var obj1 = Pool.GetObject();
            obj1.DoSomething("obj1");

            Thread.Sleep(2000);
            var obj2 = Pool.GetObject();
            obj2.DoSomething("obj2");
            Pool.ReleaseObject(obj1);

            Thread.Sleep(2000);
            var obj3 = Pool.GetObject();
            obj3.DoSomething("obj3");

obj1 :  is written on 4/21/2016 11:25:26 AM
obj2 :  is written on 4/21/2016 11:25:28 AM
obj3 :  is written on 4/21/2016 11:25:26 AM

[PartCreationPolicy(CreationPolicy.Shared)]

using System;
using System.ComponentModel.Composition;

namespace SlMefTest
{
   [Export]
   public class WebServiceData
   {
       public int Result { set; get; }
      
       public WebServiceData()
       {
           var rnd = new Random();
           Result = rnd.Next();
       }
   }

}

<UserControl x:Class="SlMefTest.MainPage"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
   xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
   xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
   mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="400">
   <StackPanel>
       <Button Content="MainPageButton" Height="23"
               HorizontalAlignment="Left"
               Margin="10,10,0,0" Name="button1"
               VerticalAlignment="Top" Width="98" Click="button1_Click" />
       <StackPanel Name="panel1" Margin="5"/>
   </StackPanel>
</UserControl>

using System.ComponentModel.Composition;
using System.Windows;

namespace SlMefTest
{
   public partial class MainPage
   {
       [Import]
       public WebServiceData Data { set; get; }

       public MainPage()
       {
           InitializeComponent();
           this.Loaded += mainPageLoaded;
       }

       void mainPageLoaded(object sender, RoutedEventArgs e)
       {
           CompositionInitializer.SatisfyImports(this);
           panel1.Children.Add(new SilverlightControl1());
       }

       private void button1_Click(object sender, RoutedEventArgs e)
       {
           MessageBox.Show(Data.Result.ToString());
       }
   }
}

<UserControl x:Class="SlMefTest.SilverlightControl1"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
   xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
   xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
   mc:Ignorable="d"
   d:DesignHeight="300" d:DesignWidth="400">
  
   <Grid x:Name="LayoutRoot" Background="White">
       <Button Content="UserControlButton"
               Height="23"
               HorizontalAlignment="Left"
               Margin="10,10,0,0"
               Name="button1"
               VerticalAlignment="Top"
               Width="125"
               Click="button1_Click" />
   </Grid>
</UserControl>

using System.ComponentModel.Composition;
using System.Windows;

namespace SlMefTest
{
   public partial class SilverlightControl1
   {
       [Import]
       public WebServiceData Data { set; get; }

       public SilverlightControl1()
       {
           InitializeComponent();
           this.Loaded += silverlightControl1Loaded;
       }

       void silverlightControl1Loaded(object sender, RoutedEventArgs e)
       {
           CompositionInitializer.SatisfyImports(this);
       }

       private void button1_Click(object sender, RoutedEventArgs e)
       {
           MessageBox.Show(Data.Result.ToString());
       }
   }
}

public class FileStore
    {
        public string WorkingDirectory { get; set; }

        public string Save(int id, string message)
        {
            var path = Path.Combine(this.WorkingDirectory + id + ".txt");
            File.WriteAllText(path, message);
            return path;
        }

        public event EventHandler<MessageEventArgs> MessageRead;

        public void Read(int id)
        {
            var path = Path.Combine(this.WorkingDirectory + id + ".txt");
            var msg = File.ReadAllText(path);
            this.MessageRead(this, new MessageEventArgs { Message = msg });    
        }
    }

 public string Read(int id)
 {
     var path = Path.Combine(this.WorkingDirectory + id + ".txt");
     var msg = File.ReadAllText(path);
     this.MessageRead(this, new MessageEventArgs { Message = msg });
     return msg;
  }

public void Save(int id, string message)
{
    var path = Path.Combine(this.WorkingDirectory + id + ".txt");
    File.WriteAllText(path, message);
}

public class FileStore
    {
        public string WorkingDirectory { get; set; }

        public void Save(int id, string message)
        {
            var path = GetFileName(id);  //ok to query from Command
            File.WriteAllText(path, message);            
        }

        public string Read(int id)
        {
            var path = GetFileName(id);
            var msg = File.ReadAllText(path);
            return msg;
        }
     
        public string GetFileName(int id)
        {
            return Path.Combine(this.WorkingDirectory , id + ".txt");     
        }
    }

    // BUGBUG: I'm sure these GUIDs are defined somewhere but I'm not sure which library contains them, so defining them here.
    DEFINE_GUID(IID_IFoo, 0x12345678,0x1234,0x1234,0x12,0x12,0x12,0x12,0x12,0x12,0x12,0x12);

Tools>Options>Environment>Task List

// TODO:2008-12-06:johnc:Add support for negative offsets.
// While it is unlikely that we get a negative offset, it can
// occur if the garbage collector runs out of space.

namespace IOCBeginnerGuide
{
  class Kid
  {
      private int _age;
      private string _name;

      public Kid(int age, string name)
      {
          _age = age;
          _name = name;
      }

      public override string ToString()
      {
          return "KID's Age: " + _age + ", Kid's Name: " + _name;
      }
  }
}

using System;

namespace IOCBeginnerGuide
{
  class Parent
  {
      private int _age;
      private string _name;
      private Kid _obj;

      public Parent(int personAge, string personName, int kidsAge, string kidsName)
      {
          _obj = new Kid(kidsAge, kidsName);
          _age = personAge;
          _name = personName;
      }

      public override string ToString()
      {
          Console.WriteLine(_obj);
          return "ParentAge: " + _age + ", ParentName: " + _name;
      }
  }
}

using System;

namespace IOCBeginnerGuide
{
  class Program
  {
      static void Main(string[] args)
      {
          Parent p = new Parent(35, "Dev", 6, "Len");
          Console.WriteLine(p);

          Console.ReadKey();
          Console.WriteLine("Press a key...");
      }
  }
}

KID's Age: 6, Kid's Name: Len
ParentAge: 35, ParentName: Dev

//IBuisnessLogic.cs
namespace IOCBeginnerGuide
{
  public interface IBuisnessLogic
  {
  }
}

//Kid.cs
namespace IOCBeginnerGuide
{
  class Kid : IBuisnessLogic
  {
      private int _age;
      private string _name;

      public Kid(int age, string name)
      {
          _age = age;
          _name = name;
      }

      public override string ToString()
      {
          return "KID's Age: " + _age + ", Kid's Name: " + _name;
      }
  }
}

//Parent.cs
using System;

namespace IOCBeginnerGuide
{
  class Parent
  {
      private int _age;
      private string _name;
      private IBuisnessLogic _refKids;

      public Parent(int personAge, string personName, IBuisnessLogic obj)
      {          
          _age = personAge;
          _name = personName;
          _refKids = obj;
      }

      public override string ToString()
      {
          Console.WriteLine(_refKids);
          return "ParentAge: " + _age + ", ParentName: " + _name;
      }
  }
}

//CIOC.cs
using System;

namespace IOCBeginnerGuide
{
  class CIOC
  {
      Parent _p;

      public void FactoryMethod()
      {
          IBuisnessLogic objKid = new Kid(12, "Ren");
          _p = new Parent(42, "David", objKid);
      }

      public override string ToString()
      {
          Console.WriteLine(_p);          
          return "Displaying using Constructor Injection";
      }
  }
}

//Program.cs
using System;

namespace IOCBeginnerGuide
{
  class Program
  {
      static void Main(string[] args)
      {
          CIOC obj = new CIOC();
          obj.FactoryMethod();
          Console.WriteLine(obj);

          Console.ReadKey();
          Console.WriteLine("Press a key...");
      }
  }
}

//Parent.cs
using System;

namespace IOCBeginnerGuide
{
  class Parent
  {
      private int _age;
      private string _name;

      public Parent(int personAge, string personName)
      {          
          _age = personAge;
          _name = personName;
      }

      public IBuisnessLogic RefKID {set; get;}

      public override string ToString()
      {
          Console.WriteLine(RefKID);
          return "ParentAge: " + _age + ", ParentName: " + _name;
      }
  }
}

//CIOC.cs
using System;

namespace IOCBeginnerGuide
{
  class CIOC
  {
      Parent _p;

      public void FactoryMethod()
      {
          IBuisnessLogic objKid = new Kid(12, "Ren");
          _p = new Parent(42, "David");
          _p.RefKID = objKid;
      }

      public override string ToString()
      {
          Console.WriteLine(_p);          
          return "Displaying using Setter Injection";
      }
  }
}

CREATE TABLE Comments (
comment_idSERIAL PRIMARY KEY,
parent_idBIGINT UNSIGNED,
comment TEXT NOT NULL,
FOREIGN KEY (parent_id) REFERENCES Comments(comment_id)
);

UPDATE Comments SET parent_id = 3 WHERE comment_id = 6;

SELECT parent_id FROM Comments WHERE comment_id = 6; -- returns 4
UPDATE Comments SET parent_id = 4 WHERE parent_id = 6;
DELETE FROM Comments WHERE comment_id = 6;

  WITH CommentTree (comment_id, bug_id, parent_id, author, comment, depth)
AS (
SELECT *, 0 AS depth FROM Comments
WHERE parent_id IS NULL
UNION ALL
SELECT c.*, ct.depth+1 AS depth FROM CommentTreect
JOIN Comments c ON (ct.comment_id = c.parent_id)
)
SELECT * FROM CommentTree WHERE bug_id = 1234;

SELECT * FROM Comments
START WITH comment_id = 9876
CONNECT BY PRIOR parent_id = comment_id;

  CREATE TABLE Comments ( comment_id SERIAL PRIMARY KEY,
path VARCHAR(1000),
bug_id BIGINT UNSIGNED NOT NULL,
author BIGINT UNSIGNED NOT NULL,
comment_date DATETIME NOT NULL,
comment TEXT NOT NULL,
FOREIGN KEY (bug_id) REFERENCES Bugs(bug_id),
FOREIGN KEY (author) REFERENCES Accounts(account_id)

  SELECT * FROM Comments AS c
WHERE '1/4/6/7/' LIKE c.path || '%' ;

  SELECT * FROM Comments AS c
WHERE c.path LIKE '1/4/' || '%' ;

  CREATE TABLE Comments ( comment_id SERIAL PRIMARY KEY,
nsleft INTEGER NOT NULL,
nsright INTEGER NOT NULL,
bug_id BIGINT UNSIGNED NOT NULL,
author BIGINT UNSIGNED NOT NULL,
comment_date DATETIME NOT NULL,
comment TEXT NOT NULL,
FOREIGN KEY (bug_id) REFERENCES Bugs (bug_id),
FOREIGN KEY (author) REFERENCES Accounts(account_id)
);

شماره‌ی سمت چپ یک گره از تمام شماره‌های سمت چپ فرزندان آن گره کوچک‌تر و شماره‌ی سمت راست آن گره از تمام شماره‌های سمت راست آن گره بزرگ‌تر است. این شماره‌ها هیچ ارتباطی به comment_id مربوط به آن گره ندارند.

یک راه حل ساده برای تخصیص این شماره‌ها به گره‌ها این است که از سمت چپ یک گره آغاز می‌کنیم و اولین شماره را اختصاص می‌دهیم و به همین به گره‌ای سمت چپ فرزندان می‌آییم و شماره‌ها را به صورت افزایشی به سمت چپ آن‌ها نیز اختصاص می‌دهیم. سپس در ادامه به سمت راست آخرین نود رفته و از آن جا به سمت بالا می‌آییم و به همین ترتیب به صورت بازگشتی تخصیص شماره‌ها را ادامه می‌دهیم.

با اختصتص شماره‌ها به هر گره، می‌توان از آن‌ها برای یافتن نیاکان و فرزندان آن گره بهره جست. برای مثال برای بازیابی گره‌ی 4 و فرزندان (نوه‌های) آن باید دنبال گره‌هایی باشیم که شماره‌های آن گره‌ها بین nsleft و nsright گره‌ی شماره‌4 باشد:

  SELECT c2.* FROM Comments AS c1
JOIN Comments as c2
ON c2.nsleft BETWEEN c1.nsleft AND c1.nsright
WHERE c1.comment_id = 4;

به جای استفاده از جدول Comments برای ذخیره‌ی اطلاعات مربوط به یک درخت از جدول TreePath استفاده می‌کنیم. به ازای هر یک جفت گره در این درخت یک سطر در جدول ذخیره می‌شود که ارتباط پدر فرزندی را نمایش می‌دهد و الزاما نباید این دو پدر فرزند بلافصل باشد. همچنین یک سطر هم به ازای ارتباط هر گره با خودش به جدول اضافه می‌گردد.

پرس‌وجوهای بازیابی نیاکان و فرزندان (گره‌ها) از طریق جدول TreePaths ساده‌تر از روش مجموعه‌های تودرتو است. مثلا برای بازیابی فرزندان (نوه‌های) گره‌ی شماره‌ی 4، سطرهایی که نیاکان آن‌ها 4 است را به دست می‌آوریم:

   SELECT c.*  FROM Comments AS c
JOIN TreePaths AS t ON c.comment_id = t.descendant
WHERE t.ancestor = 4;

   public interface IFilesService
    {
        DirectoryInfo GetDirectoryInfo(string directoryPath);
        void DeleteFile(string fileName);
        void WritePersonInFile(string fileName,string name, string lastName, byte age);
    }

    class FilesServices:IFilesService
    {
        public DirectoryInfo GetDirectoryInfo(string directoryPath)
        {
            return new DirectoryInfo(directoryPath);
        }

        public void DeleteFile(string fileName)
        {
            File.Delete(fileName);
            Console.WriteLine("the file has been deleted");
        }

        public void WritePersonInFile(string fileName, string name, string lastName, byte age)
        {
            var text = $"my name is {name} {lastName} with {age} years old from dotnettips.info";
            File.WriteAllText(fileName,text);
        }    
    }

    class FilesServicesProxy:IFilesService
    {
        private readonly IFilesService _filesService;

        public FilesServicesProxy()
        {
            _filesService=new FilesServices();
        }

        public DirectoryInfo GetDirectoryInfo(string directoryPath)
        {
            var existing = Directory.Exists(directoryPath);
            if (!existing)
                Directory.CreateDirectory(directoryPath);
            return _filesService.GetDirectoryInfo(directoryPath);
        }

        public void DeleteFile(string fileName)
        {
            if(!File.Exists(fileName))
                Console.WriteLine("Please enter a valid path");
            else
                _filesService.DeleteFile(fileName);
        }

        public void WritePersonInFile(string fileName, string name, string lastName, byte age)
        {
            if (!Directory.Exists(fileName.Remove(fileName.LastIndexOf("\\"))))
            {
                Console.WriteLine("File Path is not valid");
                return;
            }
            if (name.Trim().Length == 0)
            {
                Console.WriteLine("first name must enter");
                return;
            }

            if (lastName.Trim().Length == 0)
            {
                Console.WriteLine("last name must enter");
                return;
            }

            if (age<18)
            {
                Console.WriteLine("your age is illegal");
                return;
            }


            if (name.Trim().Length < 3)
            {
                Console.WriteLine("first name must be more than 2 letters");
                return;
            }

            if (lastName.Trim().Length <5)
            {
                Console.WriteLine("last name must be more than 4 letters");
                return;
            }

            _filesService.WritePersonInFile(fileName,name,lastName,age);
            Console.WriteLine("the file has been written");
        }
    }

static void Main(string[] args)
        {
            IFilesService filesService=new FilesServicesProxy();
            filesService.WritePersonInFile("c:\\myfakepath\\a.txt","ali","yeganeh",26);

            var directory = filesService.GetDirectoryInfo("d:\\myrightpath\\");
            var fileName = Path.Combine(directory.FullName, "dotnettips.txt");

            filesService.WritePersonInFile(fileName, "al", "yeganeh", 26);
            filesService.WritePersonInFile(fileName, "ali", "yeganeh", 12);
            filesService.WritePersonInFile(fileName, "ali", "yeganeh", 26);

            filesService.DeleteFile("c:\\myfakefile.txt");
            filesService.DeleteFile(fileName);
        }

File Path is not valid
first name must be more than 2 letters
your age is illegal
the file has been written
Please enter a valid path
the file has been deleted

 public class DependencyResolver
    {
        public static void Resolve(IWindsorContainer container)
        {
            var context = new DatabaseContext("type=embedded;storesdirectory=c:\brightstar;storename=test ");
            container.Register(Component.For<IUnitOfWork>().Instance(context).LifestyleTransient());
        }
    }