Question

我正在使用ASP.Net MVC 4框架开发在线商店。

我有一个对象类别 - 商店中的商品类别（例如男士服饰）：

public class Category
{
    [Required]
    public long id { get; set; }

    [Required]
    public string name { get; set; }

    public bool active { get; set; }
    public bool displayOnTop { get; set; }
    public bool showSubcategoriesItems { get; set; }

    public Category parentCategory { get; set; }

    public virtual Collection<Item> items { get; set; }

    public Category()
    {
        this.items = new Collection<Item>();
    }
}

有一个属性parentCategory - 这意味着此类别包含在另一个类别中（例如男士服装＆gt;衬衫）。

要编辑现有的类别I，请使用以下操作：

[HttpPost]
public ActionResult EditCategory(Category editedCategory, string parentCategorySelector)
{
    UsersContext db = new UsersContext();

    Category existingCategory = db.categories.SingleOrDefault(c => c.id == editedCategory.id);
    long parentCategoryId = (long)Int32.Parse(parentCategorySelector);
    Category parentCategory = db.categories.SingleOrDefault(c => c.id == parentCategoryId);

    if (existingCategory == null) return RedirectToAction("Index", "Admin");

    existingCategory.name = editedCategory.name;
    existingCategory.active = editedCategory.active;
    existingCategory.displayOnTop = editedCategory.displayOnTop;
    existingCategory.showSubcategoriesItems = editedCategory.showSubcategoriesItems;
    existingCategory.parentCategory = parentCategory;

    db.Entry(existingCategory.parentCategory).State = EntityState.Modified;
    db.SaveChanges();

    return View(existingCategory);
}

一切正常，除非我想将parentCategory设置为null - 它在代码中设置为null，但是null值没有保存到数据库 - 之前的值仍然存在。

但如果我这样做：

[HttpPost]
public ActionResult EditCategory(Category editedCategory, string parentCategorySelector)
{
    UsersContext db = new UsersContext();

    Category existingCategory = db.categories.SingleOrDefault(c => c.id == editedCategory.id);
    long parentCategoryId = (long)Int32.Parse(parentCategorySelector);
    Category parentCategory = db.categories.SingleOrDefault(c => c.id == parentCategoryId);

    if (existingCategory == null) return RedirectToAction("Index", "Admin");

    existingCategory.name = editedCategory.name;
    existingCategory.active = editedCategory.active;
    existingCategory.displayOnTop = editedCategory.displayOnTop;
    existingCategory.showSubcategoriesItems = editedCategory.showSubcategoriesItems;
    existingCategory.parentCategory = null;

    db.Entry(existingCategory.parentCategory).State = EntityState.Modified;
    db.SaveChanges();

    return View(existingCategory);
}

即。我在没有条件的情况下将其设置为null，正确保存。

我做错了什么？

Answer 1

为什么“类别”下没有Key属性。 ID ？如果 id 是主键，则必须在那里。

您应该使用包含到load relate entities：

   [HttpPost]
    public ActionResult EditCategory(Category editedCategory, string parentCategorySelector)
    {
        using(UsersContext db = new UsersContext())
        {
            Category existingCategory = db.categories.Include(c => c.parentCategory).SingleOrDefault(c => c.id == editedCategory.id);
            long parentCategoryId = (long)Int32.Parse(parentCategorySelector);
            Category parentCategory = db.categories.SingleOrDefault(c => c.id == parentCategoryId);

            if (existingCategory == null) return RedirectToAction("Index", "Admin");

            existingCategory.name = editedCategory.name;
            existingCategory.active = editedCategory.active;
            existingCategory.displayOnTop = editedCategory.displayOnTop;
            existingCategory.showSubcategoriesItems = editedCategory.showSubcategoriesItems;
            existingCategory.parentCategory = parentCategory;

            db.SaveChanges();

            return View(existingCategory);
        }
    }

请注意，DbContext如何正确处理。

实体框架不保存对象属性

1 个答案: