Question

我也在尝试更新实体及其相关实体。例如，我有一个具有属性类别的类Car，我想更改其类别。所以，我在Controller中有以下方法：

public ActionResult Edit(int id)
    {
        var categories = context.Categories.ToList();
        ViewData["categories"] = new SelectList(categories, "Id", "Name");
        var car = context.Cars.Where(c => c.Id == id).First();
        return PartialView("Form", car);
    }

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Edit(Car car)
    {
        var category = context.Categories.Where(c => c.Id == car.Category.Id).First();
        car.Category = category;
        context.UpdateCar(car);
        context.SaveChanges();
        return RedirectToAction("Index");
    }

ObjectContext类中的UpdateCar方法如下：

public void UpdateCar(Car car)
    {
        var attachedCar = Cars.Where(c => c.Id == car.Id).First();
        ApplyItemUpdates(attachedCar, car);
    }

    private void ApplyItemUpdates(EntityObject originalItem, EntityObject updatedItem)
    {
        try
        {                
            ApplyPropertyChanges(originalItem.EntityKey.EntitySetName, updatedItem);
            ApplyReferencePropertyChanges(updatedItem, originalItem);
        }
        catch (InvalidOperationException ex)
        {
            Console.WriteLine(ex.ToString());
        }
    }        

    public void ApplyReferencePropertyChanges(IEntityWithRelationships newEntity, IEntityWithRelationships oldEntity)
    {
        foreach (var relatedEnd in oldEntity.RelationshipManager.GetAllRelatedEnds())
        {
            var oldRef = relatedEnd as EntityReference;
            if (oldRef != null)
            {
                var newRef = newEntity.RelationshipManager.GetRelatedEnd(oldRef.RelationshipName, oldRef.TargetRoleName) as EntityReference;
                oldRef.EntityKey = newRef.EntityKey;
            }
        }
    }

问题是当我在控制器中的POST之后设置Category属性时，实体状态将更改为Added而不是保留为Detached。

如何在不设置所有属性的情况下更新与Entity Framework和ASP.NET MVC的一对一关系，如this帖子一样？

Answer 1

好的人，我刚刚发现它是如何解决的。不是在Category属性中设置整个对象，而是必须在引用属性中仅设置实体键。

所以，这是错误的：

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(Car car)
{
    var category = context.Categories.Where(c => c.Id == car.Category.Id).First();
    car.Category = category;
    context.UpdateCar(car);
    context.SaveChanges();
    return RedirectToAction("Index");
}

这是正确的方法：

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(Car car)
{
    var category = context.Categories.Where(c => c.Id == car.Category.Id).First();
    car.CategoryReference.EntityKey = category.EntityKey;
    context.UpdateCar(car);
    context.SaveChanges();
    return RedirectToAction("Index");
}

ASP.NET MVC的实体框架。更新实体问题

1 个答案: