以断开连接模式删除多个实体

Question

I am working on an application (EF6 Code First approach) that is interacting with a entity/table FloorPlan and has 10 records. I want to delete first 6 records as those are obsolete with new business requirements. Here's how the table currently looks:

To delete this in the Code First approach, I tried following code in disconnected state:

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();
};

When I run update-database command via package manager console, I get following error:

The object cannot be deleted because it was not found in the ObjectStateManager.

I have also tried without changing the state of the entities but to no avail. I only want to do it in disconnected mode. Can you guys throws some pointers around this problem?

Answer 1

If you want to delete those records the only you need to do is create your entity instances with their existing Ids.

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();
};

Update

Well, in that case I suggest you make a query first seeking all the entities you want to delete by their names, and after that you can delete them using the RemoveRange method:

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

You are removing object from newdbContext.FloorPlan, buy you take them from floorPlansOld.

It looks completely wrong to me.

Try this

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