具有所需关联的实体框架4.3 [英] Entity framework 4.3 with required association

问题描述

使用EF代码优先方法和关联，我的行为非常奇怪.我有两个实体:

I'm a very strange behavior with EF code first approach and associations. I have two entities:

public class GlobalKpiSectionn
{
    public GlobalKpiSection()
    {
        this.Regions = new HashSet<Region>();
    }

    public virtual ICollection<Region> Regions { get; protected set; }  
}

public class Region
{
    public int RegionId { get; set; }

    public bool IsMain { get; set; }

    [Required]
    public virtual GlobalKpiSection KpiSection { get; set; }
}

我需要KiSection属性上的required属性，以便进行级联删除.

I need required attribute on KiSection property in order to get cascade deletes.

问题出在下面-此代码中:

The problem is the following - in this code:

var mainRegion = context.Regions.Single(x => x.RegionId == id);
mainRegion.IsMain = true;
context.SaveChanges();

我收到一个例外，该字段未初始化Required字段.但是存在只是没有加载.当我使用此实体时，我不会在任何地方写任何包含属性的显式包含内容.我该怎么做才能克服这个问题?

I'm getting exception that Required field is not initialized. But it is present just not loaded. I don't what to write everywhere explicit includes for properties when I use this entity. What can I do to overcome this?

更新

我确定其延迟加载问题的原因是:

The reason why I'm sure its lazy loading issue is that:

        var primaryRegion = context.Regions
                                   .Include(x => x.KpiSection)
                                   .Single(x => x.RegionId == id);

解决了这个问题，但是绝对可以解决.

Solves the issue, but its definitely awful solution.

推荐答案

这就是为什么您不应该使用数据注释的原因.数据注释是错误的功能，因为它们同时进行映射和验证(违反单一职责)-如您所见，它并不总是您想要的.因此，您当前的选择是:

That is why you should not use data annotations. Data annotations are wrong feature because they do both mapping and validation (violation of single responsibility) - as you see it is not always what you want. So your current options are:

• 关闭context.Configuration.ValidateOnSaveEnabled = false
中的验证
• 在您的Region实体中公开不可为空的KpiSectionId外键属性(在导航属性中不需要Required属性).
• 使用流畅的API代替数据注释:

• Turn off validation in context.Configuration.ValidateOnSaveEnabled = false
• Expose non nullable KpiSectionId foreign key property in your Region entity (you will not need Required attribute on your navigation property).
• Use fluent API instead of data annotations :

示例:

modelBuilder.Entity<GlobalKpiSection>()
            .WithMany(s => s.Regions)
            .HasRequired(r => r.KpiSection);

这篇关于具有所需关联的实体框架4.3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！