引用Model.net核心中的ApplicationUser

Question

我正在处理一个项目，我有两个对象Group和ApplicationUser，引用从Group到ApplicationUser。我的Group模型有一个属性CreatedBy，用于提供有关创建组的用户的信息。

保存组执行正确，CreatedBy将用户ID正确存储在数据库中。当我想显示组(对象(的列表时，就会出现此问题。CreatedBy属性没有被检索，而是具有null值(尽管保存了userId值(。

分组模型：

public class Group
{
public int Id { get; set; }
public string Name { get; set; }
public string Descriotion { get; set; }
public ApplicationUser CreatedBy { get; set; }
}

组控制器(具有保存和显示方法(：

public class GroupController : Controller
{
private readonly ApplicationDbContext _db;
private readonly UserManager<IdentityUser> _userManager;

public GroupController(ApplicationDbContext db, UserManager<IdentityUser> userManager)
{
_db = db;
_userManager = userManager;
}

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create([Bind("Id,Name,Descriotion")] Group @group)
{
string userId = _userManager.GetUserId(User);
var appUser = _db.ApplicationUser.Find(userId);
if (!String.IsNullOrEmpty(userId) && appUser != null)
{
group.CreatedBy = appUser;
}

if (ModelState.IsValid)
{
_db.Add(@group);
await _db.SaveChangesAsync();
return RedirectToAction(nameof(Index));
}
return View(@group);
}
public async Task<IActionResult> Groups()
{
return View("Groups", await _db.Groups.ToListAsync());
}
}

应用程序用户模型：

public class ApplicationUser : IdentityUser
{
[NotMapped]
public string RoleId { get; set; }
[NotMapped]
public string Role { get; set; }

public ApplicationUser()
{
}
}

组(模型(的迁移：

public partial class GroupsModel : Migration
{
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.CreateTable(
name: "Groups",
columns: table => new
{
Id = table.Column<int>(type: "integer", nullable: false)
.Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
Name = table.Column<string>(type: "text", nullable: true),
Descriotion = table.Column<string>(type: "text", nullable: true),
CreatedById = table.Column<string>(type: "text", nullable: false),
},
constraints: table =>
{
table.PrimaryKey("PK_Groups", x => x.Id);
table.ForeignKey(
name: "FK_Groups_AspNetUsers_CreatedById",
column: x => x.CreatedById,
principalTable: "AspNetUsers",
principalColumn: "Id",
onDelete: ReferentialAction.Restrict);
});
migrationBuilder.CreateIndex(
name: "IX_Groups_CreatedById",
table: "Groups",
column: "CreatedById");
}
protected override void Down(MigrationBuilder migrationBuilder)
{
migrationBuilder.DropTable(
name: "Groups");
}
}

我的上下文文件

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

public DbSet<ApplicationUser> ApplicationUser { get; set; }
public DbSet<Group> Groups { get; set; }

}

1.我的模型或任何其他文件中是否有问题？如何检索CreatedBy值正确的Group对象

2.有更好的方法设置CreatedBy属性吗现在我需要创建ApplicationUser对象，以便设置属性。有没有办法只提供userId(字符串(而不创建ApplicationUser？

string userId = _userManager.GetUserId(User);
var appUser = _db.ApplicationUser.Find(userId);
if (!String.IsNullOrEmpty(userId) && appUser != null)
{
group.CreatedBy = appUser;
}

Answer 1

如果你想看到，你必须包括用户

public async Task<IActionResult> Groups()
{
return View("Groups", await _db.Groups.Include(i=>i.CreatedBy).ToListAsync());
}

EF-Net5+可以简单地创建外键列，但最好将外键显式地包含在类中

public class Group
{
public int Id { get; set; }
public string Name { get; set; }
public string Descriotion { get; set; }
public string CreatedById { get; set; }
public virtual ApplicationUser CreatedBy { get; set; }
}

这样你的代码会更简单

string userId = _userManager.GetUserId(User);
if ( !string.IsNullOrEmpty(userId))  group.CreatedById = userId;