实体框架 6:将子对象添加到父列表与将子对象的导航属性设置为父对象

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问题描述

我有一个现有的数据库，其中包含两个表 MailServers 和 MailDomains.MailDomains 的外键列 MailServerId 指向 MailServers 中的 Id 主键列.所以我们这里是一对多的关系.

I have an existing database with two tables MailServers and MailDomains in it. MailDomains has the foreign key column MailServerId pointing to the Id primary key column in MailServers. So we have a one-to-many-relationship here.

我关注这篇文章并通过实体数据模型向导中的数据库优先代码"模型.这产生了以下两个 C# 类:

I followed this article and created my Entity Framework POCOs via the "Code first from database" model in the Entity Data Model Wizard. This produced the following two C# classes:

public partial class MailServer
{
    public MailServer()
    {
        MailDomains = new HashSet<MailDomain>();
    }

    public int Id { get; set; }

    public virtual ICollection<MailDomain> MailDomains { get; set; }
}



public partial class MailDomain
{
    public MailDomain()
    {
    }

    public int Id { get; set; }

    public string DomainName { get; set; }

    public int MailServerId { get; set; }
    public virtual MailServer MailServer { get; set; }
}

现在我的问题是以下两种在数据库中创建和插入新对象的方法之间是否有任何区别.

Now my question is whether there is any difference between the following two approaches of creating and inserting new objects to the database.

方法(A):将新子添加到父列表中:

Approach (A): Adding new child to the parent's list:

        var mailServer = new MailServer();
        var mailDomain = new MailDomain() {
            DomainName = "foobar.net",
        };
        mailServer.MailDomains.Add(mailDomain);

        using(var context = new MyContext){
            context.MailServers.Add(mailServer);
            context.SaveChanges();
        }

方法(B):将子级的导航属性设置为父级:

Approach (B): Setting the child's navigation property to the parent:

        var mailServer = new MailServer();
        var mailDomain = new MailDomain() {
            DomainName = "foobar.net",
            MailServer = mailServer,
        };

        using(var context = new MyContext){
            context.MailDomains.Add(mailDomain);
            context.SaveChanges();
        }

我还假设在方法 (A) 中，新的 MailDomain 实例会自动添加到集合 context.MailDomains 中，而在方法 (B) 中，新的 MailServer 实例自动添加到集合 context.MailServers.这是正确的还是我必须手动执行?

I also assume that in approach (A) the new MailDomain instance is automatically added to the collection context.MailDomains while in approach (B) the new MailServer instance is automatically added to the collection context.MailServers. Is that correct or do I have to do that manually?

我的问题是:这两种方法可以互换吗?它只是让我感到困惑，在数据库中只有一个属性/列要设置(即 MailDomains 中的外键)，而在 C# 代码中有两个属性(每个类中一个)可能是修改.

So again, my question is: are the two approaches interchangeable? It just confuses me that in the database there is only one property/column to set (namely the foreign key in MailDomains) while in the C# code there are two properties (one in each class) that could be modified.

实体框架 6:将子对象添加到父列表与将子对象的导航属性设置为父对象

问题描述

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