.NET6中EF Core通过Find/FindAsync获取嵌套对象的问题

目标详情 #

我希望使用EF Core和SQLite从数据库中检索对象及其嵌套对象成员。

预期结果与实际结果 #

目前只有基础类型能正确实例化，而嵌套对象处于默认/空状态，列表也为空。我期望EF Core能执行额外查询，完整填充对象。

错误信息 #

未抛出任何错误，仅返回无效数据。

• 删除数据库并通过EF Core重建，试图修复多次更新后出现的小问题。
• 检查数据库，确认所需的所有嵌套数据都有有效条目。
• 尝试使用原生SQL，但在表连接时抛出“某对象已被引用”的错误。

我使用Microsoft.AspNetCore.Components.DataAnnotations.Validation 3.2.0-rc1.2023.4来使用ValidateComplexObjects特性。

FullName.cs #

public class FullName
{
    public ulong ID { get; set; }
    
    #region 姓名

    [Display(
        Name = "First Name", 
        AutoGenerateField = true, 
        AutoGenerateFilter = true, 
        Description = "The first name of a person", 
        GroupName = "Name",
        Order = 2, Prompt = "Enter first name here", 
        ShortName = "FName")]
    [MinLength(3, ErrorMessage = "First name can't be shorted than 3 letters")]
    [StringLength(100)]
    [Required]
    public string FirstName { get; set; }
    
    [Display(
        Name = "Last Name", 
        AutoGenerateField = true, 
        AutoGenerateFilter = true, 
        Description = "The last name of a person", 
        GroupName = "Name",
        Order = 1, Prompt = "Enter last name here", 
        ShortName = "LName")]
    [MinLength(3, ErrorMessage = "Last name can't be shorted than 3 letters")]
    [StringLength(100)]
    [Required]
    public string LastName { get; set; }
    
    [Display(
        Name = "Middle Name", 
        AutoGenerateField = true, 
        AutoGenerateFilter = true, 
        Description = "The middle name of a person", 
        GroupName = "Name",
        Order = 50, Prompt = "Enter middle name here", 
        ShortName = "MName")]
    [MinLength(3, ErrorMessage = "Middle name can't be shorted than 3 letters")]
    [StringLength(100)]
    [Required]
    public string MiddleName { get; set; }

    public string Name => $"{FirstName} {MiddleName} {LastName}";
    #endregion

}

Track.cs #

// 记录可使用的赛道及其长度信息
public record Track(int Id, [Required] string Name, [Required]int distanceInMiles);

Person.cs #

public class Person{
   public ulong Id {get;set;}
   [ValidateComplexType]  public FullName Name {get; set;}
   [Required] public string Description {get;set;}
   [ValidateComplexType] public List<Track> FriendsName {get;set;}
}

ApplicationDbContext.cs #

public class ApplicationDbContext : IdentityDbContext
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
    }

    public DbSet<FullName> Names { get; set; }
    public DbSet<Person> Persons { get; set; }
    public DbSet<Track> Tracks { get; set; }
}

ViewPeople.razor #

@page "/Person/View/{id}"
// 项目引用
@inject ApplicationDbContext ApplicationDbContext

@if(validId){ @*Blah Blah HTML*@ }
else { "Invalid Id Requested" }

@code {
    Person person;
    
    [Parameter]
    public string id { get; set; }

    bool validId = false;

    protected override async Task OnInitializedAsync()
    {
        await base.OnInitializedAsync();
        validId = ulong.TryParse(id, out var iId);
        person = await ApplicationDbContext.Persons.FindAsync(iId);
        validId = person is not null;
    }
}

EF Core生成的表结构 #

Name表 #

Track表 #

字段：id, Name, DistanceInMiles, PersonId

Person表 #

字段：id, NameId, Description

预期与实际结果对比 #

预期结果

{ 
    Id: 1, 
    Name : 
    { 
        Id: 1, 
        FirstName: "John", 
        MiddleName: "Wittle",
        LastName: "Doe"
     },
     Description: "I am not a cadaver",
     Tracks = [
        {Id: 1, Name: "Honalulu", DistanceInMidles: 12km },
        {Id: 2, Name: "Honalulu 2", DistanceInMidles: 1km },
        {Id: 3, Name: "Honalulu 6", DistanceInMidles: 4km },
     ]
}

实际结果

{ 
    Id: 1, 
    Name : 
    { 
        Id: 0, 
        FirstName: null, 
        MiddleName: null,
        LastName: null
     },
     Description: "I am not a cadaver",
     Tracks = []
}

内容的提问来源于stack exchange，提问作者Codelyok 13