The classes and objects participating in this pattern are:
This structural code demonstrates the Facade pattern which provides a simplified and uniform interface to a large subsystem of classes.
using System;
namespace DoFactory.GangOfFour.Facade.Structural
{
/// <summary>
/// MainApp startup class for Structural
/// Facade Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
public static void Main()
{
Facade facade = new Facade();
facade.MethodA();
facade.MethodB();
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Subsystem ClassA' class
/// </summary>
class SubSystemOne
{
public void MethodOne()
{
Console.WriteLine(" SubSystemOne Method");
}
}
/// <summary>
/// The 'Subsystem ClassB' class
/// </summary>
class SubSystemTwo
{
public void MethodTwo()
{
Console.WriteLine(" SubSystemTwo Method");
}
}
/// <summary>
/// The 'Subsystem ClassC' class
/// </summary>
class SubSystemThree
{
public void MethodThree()
{
Console.WriteLine(" SubSystemThree Method");
}
}
/// <summary>
/// The 'Subsystem ClassD' class
/// </summary>
class SubSystemFour
{
public void MethodFour()
{
Console.WriteLine(" SubSystemFour Method");
}
}
/// <summary>
/// The 'Facade' class
/// </summary>
class Facade
{
private SubSystemOne _one;
private SubSystemTwo _two;
private SubSystemThree _three;
private SubSystemFour _four;
public Facade()
{
_one = new SubSystemOne();
_two = new SubSystemTwo();
_three = new SubSystemThree();
_four = new SubSystemFour();
}
public void MethodA()
{
Console.WriteLine("\nMethodA() ---- ");
_one.MethodOne();
_two.MethodTwo();
_four.MethodFour();
}
public void MethodB()
{
Console.WriteLine("\nMethodB() ---- ");
_two.MethodTwo();
_three.MethodThree();
}
}
}
This real-world code demonstrates the Facade pattern as a MortgageApplication object which provides a simplified interface to a large subsystem of classes measuring the creditworthyness of an applicant.
using System;
namespace DoFactory.GangOfFour.Facade.RealWorld
{
/// <summary>
/// MainApp startup class for Real-World
/// Facade Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Facade
Mortgage mortgage = new Mortgage();
// Evaluate mortgage eligibility for customer
Customer customer = new Customer("Ann McKinsey");
bool eligible = mortgage.IsEligible(customer, 125000);
Console.WriteLine("\n" + customer.Name +
" has been " + (eligible ? "Approved" : "Rejected"));
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Subsystem ClassA' class
/// </summary>
class Bank
{
public bool HasSufficientSavings(Customer c, int amount)
{
Console.WriteLine("Check bank for " + c.Name);
return true;
}
}
/// <summary>
/// The 'Subsystem ClassB' class
/// </summary>
class Credit
{
public bool HasGoodCredit(Customer c)
{
Console.WriteLine("Check credit for " + c.Name);
return true;
}
}
/// <summary>
/// The 'Subsystem ClassC' class
/// </summary>
class Loan
{
public bool HasNoBadLoans(Customer c)
{
Console.WriteLine("Check loans for " + c.Name);
return true;
}
}
/// <summary>
/// Customer class
/// </summary>
class Customer
{
private string _name;
// Constructor
public Customer(string name)
{
this._name = name;
}
// Gets the name
public string Name
{
get { return _name; }
}
}
/// <summary>
/// The 'Facade' class
/// </summary>
class Mortgage
{
private Bank _bank = new Bank();
private Loan _loan = new Loan();
private Credit _credit = new Credit();
public bool IsEligible(Customer cust, int amount)
{
Console.WriteLine("{0} applies for {1:C} loan\n",
cust.Name, amount);
bool eligible = true;
// Check creditworthyness of applicant
if (!_bank.HasSufficientSavings(cust, amount))
{
eligible = false;
}
else if (!_loan.HasNoBadLoans(cust))
{
eligible = false;
}
else if (!_credit.HasGoodCredit(cust))
{
eligible = false;
}
return eligible;
}
}
}
The .NET optimized code demonstrates the
same real-world situation as above but uses modern, built-in .NET features,
such as, generics, reflection, object initializers, automatic properties, etc.
You can find an example on our Singleton pattern page.
All other patterns (and much more) are available in our .NET Design Pattern Framework 4.5.
Not only does the .NET Design Pattern Framework 4.5 cover GOF and Enterprise patterns, it also includes .NET pattern architectures that reduce the code you need to write by up to 75%. This unique package will change your .NET lifestyle -- for only $79. Here's what is included:
