实体框架更新与相关实体 [英] Entity Framework Updating with Related Entity

问题描述

我正在使用EF来尝试使用ASP.NET更新实体。我正在创建一个实体，设置它的属性，然后将其传回到具有ID的单独图层上的EF，以便可以应用更改。我正在做这件事，因为我只会在实体的ID被绑定到UI控件时存储。

I'm using the EF to try to update an entity with ASP.NET. I'm creating an entity, setting it's properties then passing it back to the EF on a separate layer with the ID so the change can be applied. I'm doing this because I only store the ID of the entity when it's been bound to the UI controls.

一切都适用于标准属性，但是我无法更新产品的Category.ID（相关实体）。我尝试过EntityKey，EntityReference等几个，但是没有保存类别ID。这是我所拥有的：

Everything works for standard properties, but I can't update the Category.ID of a Product (a related entity). I've tried EntityKey, EntityReference and a few other but the category ID isn't saved. This is what I have:

Product product = new Product();
product.CategoryReference.EntityKey = new EntityKey("ShopEntities.Categories", "CategoryID", categoryId);
product.Name = txtName.Text.Trim();
... other properties
StockControlDAL.EditProduct(productId, product);

public static void EditProduct(int productId, Product product) {
 using(var context = new ShopEntities()) {
     var key = new EntityKey("ShopEntities.Products", "ProductID", productId);
     context.Attach(new Product() { ProductID = productId, EntityKey = key });
     context.AcceptAllChanges();
     product.EntityKey = key;
     product.ProductID = productId;
     context.ApplyPropertyChanges("ShopEntities.Products", product);
     context.SaveChanges();
 }
}

我真的想使用EF，但我似乎在ASP.NET中使用它有一些问题。

I really want to use the EF but I seem to be having a few problems with using it with ASP.NET.

推荐答案

这是这个问题的可接受的答案使用实体框架强调ASP.NET MVC

This is accepted answer to this question Strongly-Typed ASP.NET MVC with Entity Framework

context.AttachTo(product.GetType().Name, product);
ObjectStateManager stateMgr = context.ObjectStateManager;
ObjectStateEntry stateEntry = stateMgr.GetObjectStateEntry(model);
stateEntry.SetModified();
context.SaveChanges();

你试过了吗？

[更新后的代码不起作用]

这是我使用的小扩展属性，因此下一个代码块更容易理解： p>

This is small extension property I used so next code block is easier to understand:

public partial class Product
{
    public int? CategoryID
    {
        set
        {  
           CategoryReference.EntityKey = new EntityKey("ShopEntities.Categories", "CategoryID", value);
        }
        get
        {
            if (CategoryReference.EntityKey == null)
                return null;

            if (CategoryReference.EntityKey.EntityKeyValues.Count() > 0)
                return (int)CategoryReference.EntityKey.EntityKeyValues[0].Value;
            else
                return null;
        }
    }
}

这个时候肯定）：

System.Data.EntityKey key = new System.Data.EntityKey("ShopEntities.Products", "ProductID", productId);
        object originalItem;   

        product.EntityKey = key;
        if (context.TryGetObjectByKey(key, out originalItem))
        {
            if (originalItem is EntityObject &&
                ((EntityObject)originalItem).EntityState != System.Data.EntityState.Added)
            {
                Product origProduct = originalItem as Product;   
                origProduct.CategoryID == product.CategoryID;//set foreign key again to change the relationship status           
                context.ApplyPropertyChanges(
                    key.EntitySetName, product);

            }
        }context.SaveChanges();

肯定看起来很黑。我认为原因是因为EF关系具有作为实体的状态（修改，添加，删除），并且基于该状态EF改变外键的值或删除行，如果是多对多的关系。由于某种原因（不知道为什么），关系状态不会与财产状态相同。这就是为什么我必须在originalItem上设置CategoryReference.EntityKey，以便改变关系的状态。

For sure it's looks hacky. I think that the reason is because the EF relationships have status as entities (modified, added, deleted) and based on that status EF changes the value of foreign keys or deletes row if many to many relationship is in case. For some reason (don't know why) the relationship status is not changed the same as property status. That is why I had to set the CategoryReference.EntityKey on originalItem in order to change the status of the relationship.

这篇关于实体框架更新与相关实体的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！