Abstract factory design pattern example

gistfile1.cs

namespace DesignPatterns
{
    public abstract class AbstractPluginFactory
	{
		public static AbstractPluginFactory GetFactory(string renderer)
		{
			switch (renderer)
			{
				case "ASPX":
					return new ASPXRendererFactory();
				case "Winforms":
					return new WinformsRendererFactory();
				default:
					throw new NotSupportedException(string.Format("{0} is not supported", renderer));
			}
		}

		public abstract Renderer Renderer { get; }
	}

	public class ASPXRendererFactory : AbstractPluginFactory
	{
		private Renderer _renderer;
		public override Renderer Renderer
		{
			get
			{
				return _renderer;
			}
		}
		public ASPXRendererFactory()
		{
			// This could be a protected field in PluginFactory
			_renderer = new ASPXRenderer();
		}
	}

	public class WinformsRendererFactory : AbstractPluginFactory
	{
		private Renderer _renderer;
		public override Renderer Renderer
		{
			get
			{
				return _renderer;
			}
		}
		public WinformsRendererFactory()
		{
			// This could be a protected field in PluginFactory
			_renderer = new WinformsRenderer();
		}
	}

	public abstract class Renderer
	{
		public abstract void DrawImage(string filename);
	}

	public class WinformsRenderer : Renderer
	{
		public override void DrawImage(string filename)
		{
			// This would draw onto a canvas provided via
			// a Graphics object.
			Console.WriteLine("Drawing an image for Windows forms");
		}
	}

	public class ASPXRenderer : Renderer
	{
		public override void DrawImage(string filename)
		{
			// This would output an <img..> tag to the child controls or similar.
			Console.WriteLine("Drawing an image for ASP.NET");
		}
	}
}