C# Design Patterns: the Façade pattern

April 14, 2009

Summary

Access multiple classes in one simple to use class. This class is often static too.

Example

A common use of the Façade pattern is with data access managers, a façade class that contains only static methods for CRUD operations. Another example might be a class that handles payment in an online store. This façade class would link into multiple payment providers (paypal, visa/mastercard) as well as updating any order details in a database table. Rather than making the UI perform 10-20 lines of code, this could be done in a simple CheckoutManager.ProcessPayment(…) method.

      
        public class UserManager
      
        {
      
        	// The main implementation of IRepository would be internal to your Core/Domain project,
      
        	// so consumers of your API couldn't change the database directlry without going through
      
        	// your façade classes.
      
        	private IRepository _repository;
      
        	public UserManager()
      
        	{
      
        		_repository = new SqlRepository("some connection string from a config file");
      
        	}
      
        	public UserManager(IRepository repository)
      
        	{
      
        		_repository = repository;
      
        	}
      
        	public User GetById(Guid id)
      
        	{
      
        		return _repository.ExecuteSql<User>("SELECT * FROM User WHERE Id=@Id", id)
      
        	}
      
        	public User GetByEmail(string email)
      
        	{
      
        		return _repository.ExecuteSql<User>("SELECT * FROM User WHERE Email=@Email", email)
      
        	}
      
        	// more methods User-specific methods.
      
        }

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	public class UserManager
	{
	// The main implementation of IRepository would be internal to your Core/Domain project,
	// so consumers of your API couldn't change the database directlry without going through
	// your façade classes.
	private IRepository _repository;

	public UserManager()
	{
	_repository = new SqlRepository("some connection string from a config file");
	}

	public UserManager(IRepository repository)
	{
	_repository = repository;
	}

	public User GetById(Guid id)
	{
	return _repository.ExecuteSql<User>("SELECT * FROM User WHERE Id=@Id", id)
	}

	public User GetByEmail(string email)
	{
	return _repository.ExecuteSql<User>("SELECT * FROM User WHERE Email=@Email", email)
	}

	// more methods User-specific methods.
	}