在断开模式下删除多个实体

Question

我正在开发一个与实体/表 FloorPlan 交互并有 10 条记录的应用程序（EF6 代码优先方法）。我想删除前 6 条记录，因为它们已因新的业务需求而过时。以下是表格当前的外观：

为了在 Code First 方法中删除它，我尝试了以下处于断开状态的代码：

using (var newdbContext = new HomItUpContext())
{
    var floorPlansOld = new List<FloorPlan>
    {
        new FloorPlan { Name = "Unitech Uniworld Gardens 2", MainImageUrl = "//cdn.homitup.com/resources/featured-ideas/floor-plans/unitech_uniworld_gardens_2/profile.jpg", IsActive = true, FloorPlanIdeas = new List<FloorPlanIdea>() },
        new FloorPlan { Name = "Vatika Seven Lamps", MainImageUrl = "//cdn.homitup.com/resources/featured-ideas/floor-plans/vatika_seven_lamps/profile.jpg", IsActive = true, FloorPlanIdeas = new List<FloorPlanIdea>() },
        new FloorPlan { Name = "Bestech Park View Spa", MainImageUrl = "//cdn.homitup.com/resources/featured-ideas/floor-plans/bestech_park_view_spa/profile.jpg", IsActive = true, FloorPlanIdeas = new List<FloorPlanIdea>() },
        new FloorPlan { Name = "Imperia Esfera", MainImageUrl = "//cdn.homitup.com/resources/featured-ideas/floor-plans/imperia_esfera/profile.jpg", IsActive = true, FloorPlanIdeas = new List<FloorPlanIdea>() },
        new FloorPlan { Name = "Raheja Vedas", MainImageUrl = "//cdn.homitup.com/resources/featured-ideas/floor-plans/raheja_vedas/profile.jpg", IsActive = true, FloorPlanIdeas = new List<FloorPlanIdea>() },
        new FloorPlan { Name = "Tulip Violet Grandeur", MainImageUrl = "//cdn.homitup.com/resources/featured-ideas/floor-plans/tulip_violet_grandeur/profile.jpg", IsActive = true, FloorPlanIdeas = new List<FloorPlanIdea>() }
    };

    floorPlansOld.ForEach(a => newdbContext.FloorPlan.Remove(a));
    floorPlansOld.ForEach(a => newdbContext.Entry(a).State = System.Data.Entity.EntityState.Deleted);
    newdbContext.SaveChanges();
};

当我通过包管理器控制台运行update-database 命令时，出现以下错误：

无法删除该对象，因为它在 ObjectStateManager 中找不到。

我也尝试过不更改实体的状态，但无济于事。我只想在断开连接模式下进行。各位大神能指点一下这个问题吗？

Answer 1

如果您想删除这些记录，您唯一需要做的就是使用它们现有的 Id 创建实体实例。

using (var newdbContext = new HomItUpContext())
{
    var floorPlansOld = new List<FloorPlan>
    {   //Put here the record's Ids you want to delete
        new FloorPlan { Id=1 },
        new FloorPlan { Id=2 },
        new FloorPlan { Id=3 },
        new FloorPlan { Id=4 },
        new FloorPlan { Id=5 },
        new FloorPlan { Id=6 }
    };

    newdbContext.RemoveRange(floorPlansOld);// You can use RemoveRange method instead a foreach to call Remove method.
    newdbContext.SaveChanges();
};

更新

好吧，在这种情况下，我建议您先查询所有要删除的实体的名称，然后您可以使用RemoveRange 方法删除它们：

var names=new List<string>(){ "Unitech Uniworld Gardens 2", "Vatika Seven Lamps",...};
var entitiesToDelete=newdbContext.FloorPlan.Where(fp=>names.Contains(fp.Name));
newdbContext.RemoveRange(entitiesToDelete);
newdbContext.SaveChanges();

Answer 2

您正在从 newdbContext.FloorPlan 中删除对象，请从 floorPlansOld 中购买。

在我看来完全不对。

试试这个

var a = newdbContext.FloorPlan.First();
newdbContext.FloorPlan.Remove(a);