entity-framework – 如何使用EF更新控制器中的对象？

[HttpPost]
public ActionResult Edit(int id,FormCollection form)
{
    Car entity = new Car { Id = id };

    // This will attach the car entity to the content in the unchanged state.
    this.EntityFrameworkObjectContext.Cars.Attach(car);

    TryUpdateModel(entity,form.ValueProvider.ToXYZ()); // Can't remember the exact method signature right now

    this.EntityFrameworkObjectContext.SaveChanges();
    ...
}

将实体附加到上下文时,您基本上只是通知上下文您有一个实体,他应该注意这个实体.一旦附加了实体,上下文将跟踪对其所做的更改.

但是此方法仅适用于标量属性,因为不使用此方法更新导航属性.如果启用了外键属性(如分配给类别的产品也具有链接两者的CategoryId属性),您仍应该能够使用此方法(因为导航属性使用标量属性进行映射).

编辑：另一种方法是接受Car实例作为参数：

[HttpPost]
public ActionResult Edit(int id,Car car)
{
    Car entity = new Car { Id = id };

    // This will attach the car entity to the content in the unchanged state.
    this.EntityFrameworkObjectContext.Cars.Attach(entity);

    // It is important that the Car instance provided in the car parameter has the
    // the correct ID set. Since the ApplyCurrentValues will look for any Car in the
    // context that has the specified primary key of the entity supplied to the ApplyCurrentValues
    // method and apply it's values to those entity instance with the same ID (this
    // includes the previously attached entity).
    this.EntityFrameworkObjectContext.Cars.ApplyCurrentValues(car); 
    this.EntityFrameworkObjectContext.SaveChanges();
    ...
}

您还可以滚动自己的ModelBinder,它实际上具有对您的Entity Framework Context的引用,并查看是否在表单/查询中指定了Car.Id.如果存在ID,您可以直接从上下文中获取要更新的实体.此方法需要一些努力,因为您必须首先确保搜索ID,然后应用所有指定的属性值.如果你有兴趣,我可以给你一些考试.