管道過濾器（Pipe-And-Filter）模式（出處：http://bj007.blog.51cto.com/1701577/345677）

 按照《POSA(面向模式的軟件架構)》裏的說法，管道過濾器（Pipe-And-Filter）應該屬於架構模式，因爲它通常決定了一個系統的基本架構。管道過濾器和生產流水線類似，在生產流水線上，原材料在流水線上經一道一道的工序，最後形成某種有用的產品。在管道過濾器中，數據經過一個一個的過濾器，最後得到需要的數據。

代碼實現如下：

namespace FilterDemo 
{ 
        public enum CATAGORY { Food, Drink, Cloth, Office, Other };

        public class Goods 
        { 
                public int Price { private set; get; } 
                public CATAGORY Category { private set; get; }
                public Goods(CATAGORY category, int price) 
                { 
                        Category = category; 
                        Price = price; 
                } 
        }

        public interface Filter 
        { 
                bool Match(Goods goods); 
        }

        public class PriceRangeFilter : Filter 
        { 
                int min; 
                int max;
                public PriceRangeFilter(int min, int max) 
                { 
                        this.min = min; 
                        this.max = max; 
                }
                public bool Match(Goods goods) 
                { 
                        return (goods.Price >= min && goods.Price <= max);
                } 
        }

        public class CategoryFilter : Filter 
        { 
                CATAGORY category;
                public CategoryFilter(CATAGORY category) 
                { 
                        this.category = category; 
                }
                public bool Match(Goods goods) 
                { 
                        return (goods.Category == category); 
                } 
        }

        public class CompositeFilter : Filter 
        { 
                protected ArrayList filters = new ArrayList();
                public void AddFilters( params Filter[] filters) 
                { 
                        this.filters.AddRange(filters); 
                }
                public void AddFilter(Filter filter) 
                { 
                        this.filters.Add(filter); 
                }
                public bool Match(Goods goods) 
                { 
                        return false; 
                } 
        }

        public class AddFilter : CompositeFilter 
        { 
                public bool Match(Goods goods) 
                { 
                        foreach (Filter filter in filters) 
                        { 
                                if (!filter.Match(goods)) 
                                        return false; 
                        } 
                        return true; 
                } 
        }

        public class OrFilter : CompositeFilter 
        { 
                public bool Match(Goods goods) 
                { 
                        foreach(Filter filter in filters) 
                        { 
                                if(filter.Match(goods)) 
                                        return true; 
                        } 
                        return false; 
                } 
        } 
}

  至此，Pipe-And-Filter模式的Filter部分設計已經完成。剩下的就是設計管道，並安裝上述各種Filter