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);
}