Alan.Utils

dotNet utils library.

Install

Install-Package Alan.Utils 

Features

SQL Server Multiple Result Query

Alan.Utils.Sql.SqlServerExtentions 和 Alan.Utils.Sql.DataTableSetExtensions 提供了一些SQL Server数据库查询和DataTable转换的实用方法. 下面介绍一下将一次查询的多个集合映射到实体:

假设一个下订单的场景, 你需要先查找到用户, 然后再查找到产品和库存, 按照以前的做法需要对数据库进行三次查询. 下面是伪代码:

bool PlaceOrder(int userId, int productId, int count)
{
	//以前的写法, 比如使用Dapper.Net
    var user = connection.FindOne<User>("select * from Users where UserId = @id", new{ id = userId });
    if(user == null) return false;
    var product = connection.FindOne<Product>("select * from Products where ProductId = @id", new { id = productId} );
    if(product == null) return false;
    var warehouse = connection.FindOne<Warehouse>("select * from Warehouses where Product = @id" , new { id = productId });
    if(warehouse.Count < count) return false;

    
   //新的写法, 使用Alan.Utils.Sql
	var sql = @"
		select * from Users where UserId = @userId
		select * from Products where ProductId = @productId
		select * from Warehouse where ProductId = @productId
    ";
    var items = connection.ExQuery<User, Products, Warehouse>(sql, new { userId, productId });
    if(items.Item1.Count <= 0 || items.Item2.Count <= 0 || items.Item3.Count <=0 || items.Item4.Count <= count) return false;


	//....接下来的其他操作
}

嗯, 两种写法看上去都很像 Dapper.Net, 利用了C#扩展方法. 第二种写法对数据库只做了一次查询操作, 然后返回多个强类型的结果集, 是不是感觉比第一种快捷了很多? 例子