[英]Entity framework doesn't save object property
I'm developing online store, using ASP.Net MVC 4 framework. 我正在使用ASP.Net MVC 4框架开发在线商店。
I have an object Category — category of items in store (men's apparel — for instance): 我有一个对象Category-商店中商品的类别(例如,男装):
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>();
}
}
There is a property parentCategory — which means that this category is included to another one (Men's apparel > Shirts, for instance). 有一个parentCategory属性,这意味着该类别包含在另一个类别中(例如,男士服装>衬衫)。
For editing existing Category I use the following action: 要编辑现有的类别,请执行以下操作:
[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);
}
Everything works fine, except when I want to set parentCategory to null — it sets to null in code, but null value is not being saved to database — previous value still there. 一切正常,除非我想将parentCategory设置为null(在代码中将其设置为null,但null值未保存到数据库中),以前的值仍然存在。
But if I do it like this: 但是,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);
}
ie I set it to null without conditions, it is being saved correctly. 即我将其设置为无条件的null,它已正确保存。
What am I doing wrong? 我究竟做错了什么?
Why there is no Key attribute under Category. 为什么在类别下没有键属性。 id ? id ? If the id is a primary key it must be there. 如果id是主键,则必须在其中。
You should use Include to load relate entities : 您应该使用Include 加载相关实体 :
[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);
}
}
Please note, how DbContext is properly disposed. 请注意,如何正确处理DbContext。
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