如何与实体框架创建外键关系？

发布于 2024-07-07 08:10:56 字数 456 浏览 13 评论 0原文

我想在数据库中的一个具有几个外键关系的表上创建一个新行，但我无法了解需要进行什么顺序和什么调用。这是我到目前为止所得到的：

db.Models.Order order = DB.Models.Order.CreateOrder( apple );
order.CustomerReference.Attach( ( from c in db.Customer where c.Id == custId select c ).First() );
db.SaveChanges();

代码在第二行失败，说：

在以下情况下附加操作无效与此关联的源对象相关端位于添加、删除、或分离状态。加载的对象使用 NoTracking 合并选项是始终保持独立。

有任何想法吗？

原文

I want to create a new row in my database on a table that has a couple of foreign key relationships and I haven't been able to get a handle on what order and what calls need to be made. This is what I have so far:

db.Models.Order order = DB.Models.Order.CreateOrder( apple );
order.CustomerReference.Attach( ( from c in db.Customer where c.Id == custId select c ).First() );
db.SaveChanges();

The code is failing on the second line there, saying:

Attach is not a valid operation when
the source object associated with this
related end is in an added, deleted,
or detached state. Objects loaded
using the NoTracking merge option are
always detached.

Any ideas?

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帅气称霸 2024-07-14 08:10:56

（感谢约翰修复语法）

所以我明白了。这就是你必须做的：

db.Models.Order order = DB.Models.Order.CreateOrder( apple );
order.Customer = (from c in db.Customer where c.Id == custId select c).First();
db.SaveChanges();

我希望这对人们有帮助。

(Thanks John for the grammar fixes)

So I figured it out. This is what you have to do:

db.Models.Order order = DB.Models.Order.CreateOrder( apple );
order.Customer = (from c in db.Customer where c.Id == custId select c).First();
db.SaveChanges();

I hope that helps people.

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千紇 2024-07-14 08:10:56

为什么不使用实体引用？您的方法将导致额外的 SELECT 语句。

更好的方法是使用 CustomerReference 类和 EntityKey。

order.CustomerReference = new System.Data.Objects.DataClasses.EntityReference<Customers>();
order.CustomerReference.EntityKey = new EntityKey("ModelsEntities.Customers", "Id", custId);

Why not use entity references? Your method will cause an extra SELECT statement.

A much nicer way is to use the CustomerReference class and an EntityKey.

order.CustomerReference = new System.Data.Objects.DataClasses.EntityReference<Customers>();
order.CustomerReference.EntityKey = new EntityKey("ModelsEntities.Customers", "Id", custId);

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嗳卜坏 2024-07-14 08:10:56

这里有一些示例代码用于更新：

using (var ctx = new DataModelEntities())
{

       var result = (from p in ctx.UserRole.Where(o => o.UserRoleId == userRole.UserRoleId)
                              select p).First();

       result.RolesReference.EntityKey = new EntityKey("DataModelEntities.Roles",
                                       "RoleId", userRole.RoleId);

       result.UserRoleDescription = userRole.UserRoleDescription;      
       ctx.SaveChanges();
}

For update here is some sample code:

using (var ctx = new DataModelEntities())
{

       var result = (from p in ctx.UserRole.Where(o => o.UserRoleId == userRole.UserRoleId)
                              select p).First();

       result.RolesReference.EntityKey = new EntityKey("DataModelEntities.Roles",
                                       "RoleId", userRole.RoleId);

       result.UserRoleDescription = userRole.UserRoleDescription;      
       ctx.SaveChanges();
}

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~没有更多了~