前言

滤液器模式可以很方便地实现对一个列表中的元素进行过滤的功能，能方便地修改滤器的现实，符合开闭原则。

代码

 //过滤接口
 public interface IFilter
 {
     List<RefuseSorting> Filter(List<RefuseSorting> refuseList);
 }
 //垃圾分类
 public class RefuseSorting
 {
     private string _name;
     private string _type;
     public RefuseSorting(string name, string type)
     {
         _name = name;
         _type = type;
     }
     public string Name { get { return _name; } }
     public string Type { get { return _type; } }
 }
 //按名称过滤器
 public class NameFilter : IFilter
 {
     private string name;
     public NameFilter(string name) { this.name = name; }
     public List<RefuseSorting> Filter(List<RefuseSorting> refuseList)
     {
         List<RefuseSorting> refuseFilters = new List<RefuseSorting>();
         foreach (RefuseSorting filter in refuseList)
         {
             if (filter.Name.Equals(name))
             {
                 refuseFilters.Add(filter);
             }
         }
         return refuseFilters;
     }
 }
 //按类型过滤器
 public class TypeFilter : IFilter
 {
     private string type;
     public TypeFilter(string type)
     {
         this.type = type;
     }
     public List<RefuseSorting> Filter(List<RefuseSorting> refuseList)
     {
         List<RefuseSorting> refuseFilters = new List<RefuseSorting>();
         foreach (RefuseSorting filter in refuseList)
         {
             if (filter.Type.Equals(type))
             {
                 refuseFilters.Add(filter); 
             }
         }
         return refuseFilters;
     }
 }

internal class Program
{
    /*
     * 结构型模式：Structural Pattern
     * 过滤器模式：Filter Pattern
     */
    static void Main(string[] args)
    {
        //创建列表
        List<RefuseSorting> filters = new List<RefuseSorting>();
        filters.Add(new RefuseSorting("矿泉水瓶" , "可回收垃圾"));
        filters.Add(new RefuseSorting("废弃纸箱" , "可回收垃圾"));
        filters.Add(new RefuseSorting("厕纸", "不可回收垃圾"));
        filters.Add(new RefuseSorting("卫生纸", "不可回收垃圾"));
        filters.Add(new RefuseSorting("鱼骨头", "厨余垃圾"));
        filters.Add(new RefuseSorting("果核", "厨余垃圾"));
        filters.Add(new RefuseSorting("过期化妆品", "有害垃圾"));

        //创建过滤器
        IFilter recoverableTypeFilter = new TypeFilter("可回收垃圾");
        IFilter nameFilter = new NameFilter("过期化妆品");

        // 按类型进行过滤操作
        List<RefuseSorting> refuseTypeFilters = recoverableTypeFilter.Filter(filters);
        Console.WriteLine("Filtered refuse (Type):");
        PrintList(refuseTypeFilters);

        // 按名称进行过滤操作
        List<RefuseSorting> refuseNameFilters = nameFilter.Filter(filters);
        Console.WriteLine("Filtered refuse (Name):");
        PrintList(refuseNameFilters);

        Console.ReadLine();
    }

    //打印集合
    public static void PrintList(List<RefuseSorting> refuseList)
    {
        foreach (RefuseSorting filter in refuseList)
        {
            Console.WriteLine($"{filter.Name},{filter.Type}");
        }
    }
}

运行结果