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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace ConsoleApplication21
{
    public interface IFilterGroupSQL
    {
        string SetGroupJoinSQL(String sql);
    }

    public class CountPartyUnion : IFilterGroupSQL
    {
        public string SetGroupJoinSQL(string sql)
        {
            sql += " CountPartyUnionSQL union ";
            return sql;
        }
    }

    public class BusinessUnitUnion : IFilterGroupSQL
    {
        public string SetGroupJoinSQL(string sql)
        {
            sql += " BusinessUnitSQL union ";
            return sql;
        }
    }
    public class BusinessUnitUnion1 : IFilterGroupSQL
    {
        public string SetGroupJoinSQL(string sql)
        {
            sql += " BusinessUnitSQL1 union ";
            return sql;
        }
    }
    public class TraderUnion : IFilterGroupSQL
    {
        public string SetGroupJoinSQL(string sql)
        {

            sql += " TraderUnionSQL union ";
            return sql;
        }
    }
    public class TraderUnion1 : IFilterGroupSQL
    {
        public string SetGroupJoinSQL(string sql)
        {

            sql += " TraderUnionSQL1 union ";
            return sql;
        }
    }

    public class FilterGroupChain
    {
        public IList<IFilterGroupSQL> filterChains = new List<IFilterGroupSQL>();

        public FilterGroupChain AddFilterGroupChain(IFilterGroupSQL filter)
        {
            filterChains.Add(filter);
            return this;
        }

        public string SetGroupJoinSQL()
        {
            string s = string.Empty;
            List<string> strList = new List<string>();

            foreach (var f in filterChains)
            {
                s = f.SetGroupJoinSQL(s);
            }
            s = Regex.Replace(s, @"(\w*)(union\s)$", ReplaceMethod);
            return s;
        }

        private string ReplaceMethod(Match match)
        {
            string s = "";

            s = match.Groups[1].ToString();

            return s;
        }
    }
        ;
    class Program
    {
        static void Main(string[] args)
        {
          
            FilterGroupChain filterGroupChain=new FilterGroupChain();

            filterGroupChain.AddFilterGroupChain(new CountPartyUnion())
                .AddFilterGroupChain(new BusinessUnitUnion())
                .AddFilterGroupChain(new TraderUnion())
                .AddFilterGroupChain(new TraderUnion1())
                .AddFilterGroupChain(new BusinessUnitUnion1());
          string s=  filterGroupChain.SetGroupJoinSQL();
            Console.WriteLine(s);
            
            Console.Read();
        }
    }
}

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原文地址：http://www.cnblogs.com/kexb/p/4513161.html