Dapper总结（一）---基本CRUD操作

一、dapper是什么

　　dapper是一款轻量级的ORM(Object Relationship Mapper)，它负责数据库和编程语言之间的映射。SqlConnection,MysqlConnection,OracleConnection都是继承于DBConnection，而DBConnection又是实现了IDBConnection的接口。因为Dapper是对IDBConnection接口进行了方法扩展，比如你看到的SqlMapper.cs，所以dapper支持多数据库。

二、dapper的简单使用

0、准备的测试类

   //用户类
     public class UserInfo
     {
         public int UId { get; set; }//用户Id
         public string UserName { get; set; }//用户名
         public int Age { get; set; }//年龄
         public int RoleId { get; set; }//角色Id

     }
     //角色类
     public class RoleInfo
     {
         public int RId { get; set; }//角色Id
         public string RoleName { get; set; }//角色名
     }

1、execute方法，返回值为int类型，表示受影响行数

  　　　　//插入数据
             //单条数据插入
             int result = conn.Execute("insert into userinfo values(@username,@age,@roleid)", new
             {
                 UserName = "user1",
                 Age = ,
                 RoleId =
             });  // result=1

             //多条数据插入
             List<UserInfo> users=new List<UserInfo>(){
                  new UserInfo(){UserName="user2",Age=,RoleId=},
                  new UserInfo(){UserName="user3",Age=,RoleId=},
                  new UserInfo(){UserName="user4",Age=,RoleId=},
                                  };

             int result2 = conn.Execute("insert into userinfo values(@username,@age,@roleid)", users); // result2=3        

         //修改
             int rusultEdit = conn.Execute("update userinfo set age=25 where username=@username", new { UserName = "user0" });

        //删除
             int resultDel = conn.Execute("delete from userinfo where uid=@uid", new { UId =  });

2、Query方法，返回值为IEnumerable类型

   　 //带参数查询 例子：查询用户名为user1,年龄为20的用户
             IEnumerable<UserInfo> query1 = conn.Query<UserInfo>("select * from userinfo where age=@Age and username=@username", new{Age=20,UserName="user1"})
 
      //in查询    例子：查询年龄是20,21，或22的用户
             IEnumerable<UserInfo> query2=conn.Query<UserInfo>("select * from userinfo where age in @ages",new {ages=new int []{,,}});

      //返回多个结果集   例子：查询用户列表和角色列表
             var sql = "select * from userinfo; select * from roleinfo";
             var query3 = conn.QueryMultiple(sql);//GridReader类型
             var usesList = query3.Read<UserInfo>();//IEnumberable类型
             var roleList = query3.Read<RoleInfo>();

     //表连接查询  例子：查询用户信息和其对应的角色名
         //1、返回强类型结果
             var sql2 = @"select u.username,u.age,u.uid ,r.rolename from userinfo as u join roleinfo as r on u.roleid=r.rid";
             var result2 = conn.Query<UserInfo, RoleInfo, UserInfo>(sql2, (user, role) =>
             {
                 user.Role = role;
                 return user;
             }, splitOn: "RoleName");//splitOn参数表示分割，前边的是第一个对象的属性，后边的是第二个对象的属性

         //2、返回动态类型结果
             var result3 = conn.Query(sql2);
             foreach (var item in result3)
             {
                 Console.WriteLine("username:{0},rolename:{1}", item.username, item.rolename);
             }