List集合之间的联接

    之前学习数据库的时候总结过数据库中表和表之间的连接《数据库中多表的连接》，现在做的项目需要要调用其他系统WCF服务返回List集合，从自己系统再返回一部分集合，将这两种集合链接起来再将“连接的集合‘返回到界面。

   通过查阅资料，有两种方法可以实现List集合之间的连接：一种是利用Linq语句，另外一种是利用lamda表达式，现在总结一下：

数据实体：

    /// <summary>
    /// 考试实体
    /// </summary>
    public class Exam
    {
        public string ExamId { get; set; }
        public string ExamName { get; set; }
    }

    /// <summary>
    /// 考生实体
    /// </summary>
    public class Examinee
    {
        public string ExamineeId { get; set; }
        public string ExamineeName { get; set; }
        public string ExamId { get; set; }
    }

            //考试实体集合数据
            List<Exam> examList=new List<Exam>()
            {
                new Exam(){ExamId ="ks001",ExamName = "数学考试"},
                new Exam(){ExamId ="ks002",ExamName = "语文考试"},
                new Exam(){ExamId ="ks003",ExamName = "英语考试"},
            };

            //考生实体集合数据
            List<Examinee> examineeList = new List<Examinee>()
            {
                new Examinee(){ExamineeId = "xs1001",ExamineeName="小明",ExamId ="ks001",},    
                new Examinee(){ExamineeId = "xs1002",ExamineeName="小张",ExamId ="ks001",},    
                new Examinee(){ExamineeId = "xs1003",ExamineeName="小李",ExamId ="ks002",},
            };

利用Linq语句

            var joinList = from examEtity in examList
                join examineeEntity in examineeList
                    on examEtity.ExamId equals examineeEntity.ExamId
                select new
                {
                    考试ID=examEtity.ExamId,
                    考试名称=examEtity.ExamName,
                    考生ID=examineeEntity.ExamineeId,
                    考生名称 = examineeEntity.ExamineeName
                };

            dataGridView1.DataSource = joinList.ToList();

利用lamda表达式

            var joinList = examList.Join(examineeList,examEntity=>examEntity.ExamId,
                examineeEntity => examineeEntity.ExamId, (examEntity,examineeEntity)=>
                new
                {
                    考试ID = examEntity.ExamId,
                    考试名称 = examEntity.ExamName,
                    考生ID = examineeEntity.ExamineeId,
                    考生名称 = examineeEntity.ExamineeName
                }); 

            dataGridView1.DataSource = joinList.ToList();

    
总结：

    这两种方式只是对于两个数据集合的内连接操作，还有左右连接、分组连接等等。那些还需要进一步的学习。

源码地址：http://download.csdn.net/detail/suneqing/8307283

2楼ZHOUCHAOQIANG2小时前

感觉Linq更符合变成的习惯 FROM**** iN 而不像 SQL select *** from

1楼u010539352昨天 17:12

在实践中提高的速度就是快啊