EF代码优先：如何加载相关数据（父子孙）？

发布于 2024-12-06 03:43:46 字数 489 浏览 1 评论 0原文

我有这个实体：

public class DynamicPage {

    public int PageId { get; set; }

    public int Order { get; set; }

    public string MenuText { get; set; }

    public string MenuHover { get; set; }

    public int? ParentId { get; set; }

    public virtual DynamicPage Parent { get; set; }

    public virtual ICollection<DynamicPage> Children { get; set; }
}

这个实体可能有 3 个级别：父级 ->儿童->孙子。如何加载所有关联子项（级别 2）的父项（级别 1）以及每个子项、关联孙子项（级别 3）（如果有）？谢谢帮忙。

原文

I have this entity:

public class DynamicPage {

    public int PageId { get; set; }

    public int Order { get; set; }

    public string MenuText { get; set; }

    public string MenuHover { get; set; }

    public int? ParentId { get; set; }

    public virtual DynamicPage Parent { get; set; }

    public virtual ICollection<DynamicPage> Children { get; set; }
}

This entity may have 3 level: Parent -> Child -> Grandchild. How can I load the Parent (level 1) whit all associated children (level 2) and for each child, associated grandchild (level 3) if any? Thanks to help.

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苦行僧 2024-12-13 03:43:46

EF 4.1 功能和语法：

var entity = context.Parents
    .Include(p => p.Children.Select(c => c.GrandChildren))
    .FirstOrDefault(p => p.Id == 1); // or whatever condition

EF 4.1 feature and syntax:

var entity = context.Parents
    .Include(p => p.Children.Select(c => c.GrandChildren))
    .FirstOrDefault(p => p.Id == 1); // or whatever condition

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网名女生简单气质 2024-12-13 03:43:46

如果您想让自己的生活变得轻松，请遵循 EF Code First 约定，将表 ID 命名为 Id（或者，表名称 + Id，例如， DyanmicPageId）。

这应该给您留下类似这样的结果：

public class DynamicPage
{
    public int Id { get; set; }
    public int Order { get; set; }
    public string MenuText { get; set; }
    public string MenuHover { get; set; }
    public int? ParentId { get; set; }

    public virtual DynamicPage Parent { get; set; }
    public virtual ICollection<DynamicPage> Children { get; set; }
}

然后您需要在 DbContext 类的 OnModelCreating 方法中显式设置父级和子级之间的关系。

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<DynamicPage>()
        .HasMany(page => page.Children)
        .WithRequired(child => child.Parent)
        .HasForeignKey(child => child.ParentId);
}

然后，您可以根据需要选择子代或孙代：

var parent = dbContext.DynamicPages.Where(page => page.ParentId == null);
var children = parent.Children;
var grandchildren = parent.SelectMany(page => page.Children);
var allRelatedPages = parent.Union(children).Union(grandchildren);

If you want to make life easy on yourself, follow the EF Code First conventions of naming your table IDs simply Id (or, alternatively, name of table + Id, e.g., DyanmicPageId).

This should leave you with something like this:

public class DynamicPage
{
    public int Id { get; set; }
    public int Order { get; set; }
    public string MenuText { get; set; }
    public string MenuHover { get; set; }
    public int? ParentId { get; set; }

    public virtual DynamicPage Parent { get; set; }
    public virtual ICollection<DynamicPage> Children { get; set; }
}

Then you need to set up the relationship between parents and children explicitly in an OnModelCreating method in your DbContext class.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<DynamicPage>()
        .HasMany(page => page.Children)
        .WithRequired(child => child.Parent)
        .HasForeignKey(child => child.ParentId);
}

You can then select children or grandchildren as needed:

var parent = dbContext.DynamicPages.Where(page => page.ParentId == null);
var children = parent.Children;
var grandchildren = parent.SelectMany(page => page.Children);
var allRelatedPages = parent.Union(children).Union(grandchildren);

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