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

Question

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.我已经堆叠了!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>

Answer 1

您可以尝试如下所示.

注意:您必须先提取数据然后执行映射,否则您将不会遇到此问题.

原因:当您遍历query(IQueryable)的结果时,您将lazy loading在迭代内触发加载的实体.换句话说,在单个连接上执行多个数据检索命令.

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

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