design pattern

• singleton
  Generates only one single instance at runtime.

  using System;
  
  namespace Core
  {
  	/// <summary>
  	/// The factory.
  	/// Its purpose is to create the required checking object for the actual dataset.
  	/// </summary>
  	public class ASingleton
  	{
  
  		private static ASingleton self;
  
  		/// <summary>
  		/// Constructor.
  		/// </summary>
  		private ASingleton()
  		{
  		}
  
  		/// <summary>
  		/// This function returns the only instance and creates it if required.
  		/// </summary>
  		/// <returns>the instance.</returns>
  		public static volatile ASingleton GetInstance()
  		{
  			/// Test if there is an instance
  			if( self == null )
  				lock( typeof( this ))
  					self = new ASingleton();
  
  			return self;
  		}
  
  	}
  }
  

• factory
  Returns a specific subclass depending on the parameter.

  using System;
  
  namespace Core
  {
  	/// <summary>
  	/// The factory.
  	/// Its purpose is to create the required checking object for the actual dataset.
  	/// </summary>
  	public class ACheckFactory
  	{
  
  		/// <summary>
  		/// Constructor.
  		/// </summary>
  		public ACheckFactory()
  		{
  		}
  
  		/// <summary>
  		/// This function creates and returns the required checker object.
  		/// </summary>
  		/// <param name="ds">the dataset to be checked.</param>
  		/// <returns>the checker that will do the job.</returns>
  		public ACheckBase GetChecker(AODataSet ds)
  		{
  			/// Test if Dataset is Intern or Extern 
  			/// it will create different derivates of ACheckBase
  			if( ds.isExtern )
  				return new ACheckExtern(ds);
  			else
  				return new ACheckIntern(ds);
  		}
  
  	}
  }
  

• adapter
  Interfaceadaption