标签:turn lis csharp select result set ring 列表 open
Dapper的多表查询实现
打开链接
using (var conn = new SqlConnection(myConnectionString)) { conn.Open(); .... }
单表查询
public class Account { public int? Id {get;set;} public string Name {get;set;} public string Address {get;set;} public string Country {get;set;} public int ShopId {get; set;} }
返回列表
IEnumerable<Account> resultList = conn.Query<Account>(@"
SELECT * FROM Account WHERE shopId = @ShopId", new { ShopId = shopId });
返回单个对象
Account result = conn.Query<Account>(@" SELECT * FROM Account WHERE Id = @Id", new { Id = Id }).FirstOrDefault();
返回dynamic
dynamic account = conn.Query<dynamic>(@" SELECT Name, Address, Country FROM Account WHERE Id = @Id", new { Id = Id }).FirstOrDefault();
嵌有单个对象
public class Account { public int? Id {get;set;} public string Name {get;set;} public string Address {get;set;} public string Country {get;set;} public int ShopId {get; set;} public Shop Shop {get;set;} } public class Shop { public int? ShopId {get;set;} public string Name {get;set;} public string Url {get;set;} }
查询
var resultList = conn.Query<Account, Shop, Account>(@" SELECT a.Name, a.Address, a.Country, a.ShopId s.ShopId, s.Name, s.Url FROM Account a INNER JOIN Shop s ON s.ShopId = a.ShopId ", (a, s) => { a.Shop = s; return a; }, splitOn: "ShopId" ).AsQueryable();
嵌有列表对象
public class Shop { public int? Id {get;set;} public string Name {get;set;} public string Url {get;set;} public int ShopId {get;set;} public IList<Account> Accounts {get;set;} } public class Account { public int? Id {get;set;} public string Name {get;set;} public string Address {get;set;} public string Country {get;set;} public int ShopId {get;set;} }
var lookup = new Dictionary<int, Shop>() conn.Query<Shop, Account, Shop>(@" SELECT s.*, a.* FROM Shop s INNER JOIN Account a ON s.ShopId = a.ShopId ", (s, a) => { Shop shop; if (!lookup.TryGetValue(s.Id, out shop)) { lookup.Add(s.Id, shop = s); } if (shop.Accounts == null) shop.Accounts = new List<Account>(); shop.Accounts.Add(a); return shop; }, ).AsQueryable(); var resultList = lookup.Values;
标签:turn lis csharp select result set ring 列表 open
原文地址:https://www.cnblogs.com/chengNet/p/14745763.html