Adapter Design Pattern

Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible interfaces. .NET developers write classes that expose methods that are called by clients. Most of the time they will be able to control the interfaces, but there are situations, for example, when using 3rd party libraries, where they may not be able to do so. The 3rd party library performs the desired services.

using System;

namespace PAtterns
{
/// <summary>
/// MainApp startup class for the .NET optimized
/// Adapter Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Non-adapted chemical compound
Compound unknown = new Compound(Chemical.Unknown);
unknown.Display();

// Adapted chemical compounds
Compound water = new RichCompound(Chemical.Water);
water.Display();

Compound benzene = new RichCompound(Chemical.Benzene);
benzene.Display();

Compound ethanol = new RichCompound(Chemical.Ethanol);
ethanol.Display();

// Wait for user
Console.ReadKey();
}
}

/// <summary>
/// The 'Target' class
/// </summary>
class Compound
{
// Constructor
public Compound(Chemical chemical)
{
this.Chemical = chemical;
}

// Automatic properties
public Chemical Chemical { get; set; }
public float BoilingPoint { get; set; }
public float MeltingPoint { get; set; }
public double MolecularWeight { get; set; }
public string MolecularFormula { get; set; }

public virtual void Display()
{
Console.WriteLine("\nCompound: {0} -- ", Chemical);
}
}

/// <summary>
/// The 'Adapter' class
/// </summary>
class RichCompound : Compound
{
private ChemicalDatabank _bank;

// Constructor
public RichCompound(Chemical chemical) : base(chemical) {}

public override void Display()
{
// The Adaptee
_bank = new ChemicalDatabank();

// Adaptee request methods
BoilingPoint = _bank.GetCriticalPoint(Chemical, State.Boiling);
MeltingPoint = _bank.GetCriticalPoint(Chemical, State.Melting);
MolecularWeight = _bank.GetMolecularWeight(Chemical);
MolecularFormula = _bank.GetMolecularStructure(Chemical);

base.Display();
Console.WriteLine(" Formula: {0}", MolecularFormula);
Console.WriteLine(" Weight : {0}", MolecularWeight);
Console.WriteLine(" Melting Pt: {0}", MeltingPoint);
Console.WriteLine(" Boiling Pt: {0}", BoilingPoint);
}
}

/// <summary>
/// The 'Adaptee' class
/// </summary>
class ChemicalDatabank
{
// The databank 'legacy API'
public float GetCriticalPoint(Chemical compound, State point)
{
// Melting Point
if (point == State.Melting)
{
switch (compound)
{
case Chemical.Water: return 0.0f;
case Chemical.Benzene: return 5.5f;
case Chemical.Ethanol: return -114.1f;
default: return 0f;
}
}
// Boiling Point
else
{
switch (compound)
{
case Chemical.Water: return 100.0f;
case Chemical.Benzene: return 80.1f;
case Chemical.Ethanol: return 78.3f;
default: return 0f;
}
}
}

public string GetMolecularStructure(Chemical compound)
{
switch (compound)
{
case Chemical.Water: return "H20";
case Chemical.Benzene: return "C6H6";
case Chemical.Ethanol: return "C2H5OH";
default: return "";
}
}

public double GetMolecularWeight(Chemical compound)
{
switch (compound)
{
case Chemical.Water: return 18.015;
case Chemical.Benzene: return 78.1134;
case Chemical.Ethanol: return 46.0688;
}
return 0d;
}
}


/// <summary>
/// Chemical enumeration
/// </summary>
public enum Chemical
{
Unknown,
Water,
Benzene,
Ethanol
}

/// <summary>
/// State enumeration
/// </summary>
public enum State
{
Boiling,
Melting
}
}