c# – 实体框架已经有一个与此命令关联的开放DataReader,必须先关闭它

我正在努力解决上面的错误.我在这里发现了不同的答案(堆栈溢出),但它们都没有解决我与错误相关的问题.

我只是在我的ConnectionString中启用MARS但没有成功.

我有一类产品

public class Product
{
    public Product()
    {
        this.Additives = new HashSet<Additive>();
    }

    public int Id { get; set; }
    public string Name { get; set; } // refrigerante
    public string CommercialName { get; set; } // nome popular, ex: fanta laranja
    public string Brand { get; set; } // marca, ex: Coca-cola
    public string Details { get; set; } // composicao, ingredientes
    public HalalState HalalState { get; set; } // estado: halal, haram ou desconhecido
    public DateTime? LastUpdate { get; set; } // date e hora do registo

    public virtual ICollection<Additive> Additives { get; set; } // aditivos
    public int ProviderID { get; set; }
}

}

和类添加剂代表产品中的添加剂

using System;
using System.Collections.Generic;

namespace Teknowhow.EatHalal.Core.Models
{
    public class Additive
    {
        public Additive()
        {
            this.Products = new HashSet<Product>();
        }

        public int Id { get; set; }
        public string Key { get; set; } // codigo ex: E130
        public string NamePT { get; set; } // nome ex: Acido ascorbico (Vitamina C) em portugues
        public string NameEN { get; set; } // nome ex: Acido ascorbico (Vitamina C) em inglês
        public string Details { get; set; } // detalhes sobre o aditivo, incluindo.
        public HalalState HalalState; // estado: halal, haram ou desconhecido
        public DateTime? LastUpdate { get; set; } // date e hora do registo

        public virtual ICollection<Product> Products { get; set;}
    }
}

我正在编写一个代码来实现ProductRepository上的方法,以便获得具有特定添加剂的产品.

public ICollection<Product> GetProductsByAdditive(string key)
{
    var products = context.Products;
    var productsAdditives = new List<Product>();

     foreach (var p in products)
     {
         var additives = p.Additives;

         foreach (var a in additives)
         {
             if (a.Key.Equals(key))
                productsAdditives.Add(p);   

         }
    }

    return productsAdditives.ToList();
    //TODO: um Metodo úinico que permite pesquisa por nome em PT e EN e codigo 

}

错误发生在第一个foreach循环之后,在此语句上：

var additives = p.Additives;

PS：我正在使用EF 6.
我堆积了！请帮忙！

继承人我的联系

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
        <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    </configSections>
    <connectionStrings>
    <add name="EatHalal" 
         providerName="System.Data.SqlClient" 
         connectionString="Server=192.168.1.150;Database=EatHalal;User Id=user;Password=password;MultipleActiveResultSets=true;"
             />
  </connectionStrings>
</configuration>

解决方法:

context.Products.Where(x=>x.Additives.Any(y=>y.Key==key)).ToList();

你的代码失败了,因为你在添加产品时懒惰加载添加剂……

但是itteration本身是无稽之谈…如果你想在数据库中搜索某些东西,让数据库通过给它搜索一些东西来完成它的工作,而不是告诉它给你所有东西,然后整理出你想要的东西. ..

想象一下,如果你的桌子里会有几亿件产品……

你会加载所有产品并经历多年…

看看LINQ

看看.Where()

看看.选择()

熟悉lambda表达式

标签：c,sql-server,entity-framework,lazy-loading,eager-loading
来源： https://codeday.me/bug/20190716/1475042.html