由于这个错误，我在测试我的应用程序时遇到了问题，特别是The seed entity for entity type 'Artikal' cannot be added because there was no value provided。
问题在于，肯定是通过字典paroviTip和类Tip本身提供了值（表示Artikal类中的FK）。
我想使用modelBuilder扩展（这是.NET Core 2.2的正确方法）将一些数据播种到数据库中，但是由于这个特殊错误，无法添加迁移。
我几乎用完了所有选项，因此我需要对代码进行外部查看。
填充数据库的ModelBuilderExtensions：
using BestDeal.Models;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using System;
using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace BestDeal.AdapteriPodataka
{
public static class ModelBuilderExtensions
{
public static void PopuniBazu(this ModelBuilder modelBuilder)
{
modelBuilder.Entity<Artikal>().HasData
(
new Artikal
{
NazivArtikla = "HP 250 G6",
CijenaArtikla = 700,
IdArtikla = 1,
KratkiOpis = "Vrhunski laptop za prosječnog korisnika!",
DetaljniOpis = "Povežite se sa cijenjenim HP 250 notebook računarima. Završajite poslovne zadatke sa Intel® tehnologijom, osnovnim alatima za saradnju koji su učitani na HP 250. Izdržljiva šasija pomaže zaštiti laptopa od strogosti dana.",
URLMaleSlike1 = "https://static.toiimg.com/photo/60104728/HP-15-BS542TU-2EY84PA-Laptop-Core-i3-6th-Gen4-GB1-TBDOS.jpg",
URLSlike1 = "https://images-na.ssl-images-amazon.com/images/I/81iq991JMEL._SL1500_.jpg",
TipArtikla = ParoviTip["Laptopi"],
tipNaziv = "Laptopi"
}/*There is 30 of these, shortened for easier overview*/
);
}
private static Dictionary<string, Tip> paroviTip = new Dictionary<string, Tip>();
public static Dictionary<string, Tip> ParoviTip
{
get
{
if (paroviTip.Count==0)
{
var listaTipova = new Tip[]
{
new Tip { Ime = "Laptopi", idTipa = 1 },
new Tip { Ime = "Mobiteli", idTipa = 2 },
new Tip { Ime = "Računari", idTipa = 3 },
new Tip { Ime = "Računarska oprema", idTipa = 4 }
};
foreach (Tip tipcic in listaTipova)
{
paroviTip.Add(tipcic.Ime, tipcic);
}
}
return paroviTip;
}
}
}
}
上下文文件：
using BestDeal.AdapteriPodataka;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace BestDeal.Models
{
//TODO: Skontati koji context ide, identitymodel, No authorization problem
// You can add profile data for the user by adding more properties to your IdentityUser class, please visit http://go.microsoft.com/fwlink/?LinkID=317594 to learn more.
//IdentityDbContext<IdentityUser> ???
public class BestDealContext : IdentityDbContext<IdentityUser>
{
//automatske migracije
private static readonly bool[] _migrated = { false };
public BestDealContext(DbContextOptions<BestDealContext> options) : base(options)
{
/* if (!_migrated[0])
lock (_migrated)
if (!_migrated[0])
{
Database.Migrate(); // apply all migrations
_migrated[0] = true;
}*/
// Database.ExecuteSqlCommand("SET IDENTITY_INSERT Artikal ON");
}
public DbSet<IdentityUser> IdentityUser { get; set; }
public DbSet<KorpaInfo> KorpaInfo { get; set; }
public DbSet<Narudzba> Narudzba { get; set; }
public DbSet<Obavijest> Obavijest { get; set; }
public DbSet<ChatObavijest> ChatObavijest { get; set; }
public DbSet<NarudzbeObavijest> NarudzbeObavijest { get; set; }
public DbSet<Recenzija> Recenzija { get; set; }
// public DbSet<StanjeNarudzbe> StanjeNarudzbe { get; set; }
public DbSet<Tip> Tip { get; set; }
// public DbSet<Tipovi> Tipovi { get; set; }
public DbSet<Artikal> Artikal { get; set; }
public DbSet<Korpa> Korpa { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<IdentityUser>().ToTable("IdentityUsers");
modelBuilder.Entity<Korpa>().ToTable("Korpa");
modelBuilder.Entity<KorpaInfo>().ToTable("KorpaInfo");
modelBuilder.Entity<Narudzba>().ToTable("Narudzba");
modelBuilder.Entity<Obavijest>().ToTable("Obavijest");
modelBuilder.Entity<ChatObavijest>().ToTable("ChatObavijest");
modelBuilder.Entity<NarudzbeObavijest>().ToTable("NarudzbeObavijest");
modelBuilder.Entity<Recenzija>().ToTable("Recenzija");
modelBuilder.Ignore<StanjeNarudzbe>();
modelBuilder.Entity<Tip>().ToTable("Tip");
modelBuilder.Ignore<Tipovi>();
//Database.ExecuteSqlCommand("SET IDENTITY_INSERT Artikal ON");
modelBuilder.Entity<Artikal>().ToTable("Artikal");
ModelBuilderExtensions.PopuniBazu(modelBuilder);
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
}
}
}
Artikal.cs：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Drawing.Imaging;
using System.ComponentModel.DataAnnotations;
using static System.Net.Mime.MediaTypeNames;
using System.ComponentModel.DataAnnotations.Schema;
using Microsoft.IdentityModel.Protocols;
using System.Data.SqlClient;
using System.Text;
using System.Diagnostics;
using BestDeal.AdapteriPodataka;
namespace BestDeal.Models
{
public class Artikal
{
private string nazivArtikla;
private string kratkiOpis;
private string detaljniOpis;
private string URLSlike;
private string URLMaleSlike;
private Tip tipArtikla;
double cijenaArtikla;
//TODO: Mozda lista recenzija umjesto specificne ocjene artikla, ljepse izgleda
double ocjenaArtikla;
static int id = 100;
int idArtikla = 110;
[ScaffoldColumn(false)]
private List<Recenzija> recenzije=new List<Recenzija>();
public Artikal()
{
id++;
Debug.WriteLine("dodijelio id {0}", Program.lastArtikalId);
idArtikla = Program.lastArtikalId;
Program.lastArtikalId++;
}
public Artikal(double cijenaArtikla, int idArtikla)
{
CijenaArtikla = cijenaArtikla;
this.idArtikla = idArtikla;
idArtikla = Program.lastArtikalId;
Program.lastArtikalId++;
}
String tippp;
[System.ComponentModel.DisplayName("Naziv tipa artikla")]
public String tipNaziv {
get
{
return tippp;
}
set
{
tippp = value;
/* Tip tip = new Tip();
tip.Ime = value;
Program.lastTipId++;
tip.idTipa = Program.lastTipId;
TipArtikla = tip;*/
}
}
//TODO: Ovdje bi mozda bio koristan flyweight large-scale jer slike mogu biti velike u slucaju nekoliko hiljada artikala
//public Image SlikaArtikla { get; }
[Required]
public Tip TipArtikla
{
get => tipArtikla;
set
{
//ako postoji tip ne treba dodavati novi
foreach (Tip t in Tipovi.getInstance().ListaTipova.ToList())
if (t.Equals(value)) tipArtikla = value;
else
{
/* Program.lastTipId++;
tipArtikla.idTipa = Program.lastTipId;*/
tipArtikla = value;
//ako je dodan tip koji ne postoji u listi tipova, automatski se azurira ta lista
Tipovi.getInstance().ListaTipova.Add(value);
}
}
}
[Required(ErrorMessage ="This field is required.")]
[System.ComponentModel.DisplayName("Naziv artikla")]
public string NazivArtikla { get => nazivArtikla; set => nazivArtikla = value; }
[Required(ErrorMessage = "This field is required.")]
[System.ComponentModel.DisplayName("Cijena artikla")]
public double CijenaArtikla { get => cijenaArtikla; set => cijenaArtikla = value; }
[ScaffoldColumn(false)]
[System.ComponentModel.DisplayName("Ocjena artikla")]
public double OcjenaArtikla { get => ocjenaArtikla; }// set => ocjenaArtikla = value; }
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int IdArtikla { get => idArtikla; set => idArtikla = value; }
[Required(ErrorMessage = "This field is required.")]
[System.ComponentModel.DisplayName("Kratki opis")]
public string KratkiOpis { get => kratkiOpis; set => kratkiOpis = value; }
[Required(ErrorMessage = "This field is required.")]
[System.ComponentModel.DisplayName("Detaljni opis")]
public string DetaljniOpis { get => detaljniOpis; set => detaljniOpis = value; }
[Required(ErrorMessage = "This field is required.")]
[System.ComponentModel.DisplayName("URL slike")]
public string URLSlike1 { get => URLSlike; set => URLSlike = value; }
[Required(ErrorMessage = "This field is required.")]
[System.ComponentModel.DisplayName("URL male slike")]
public string URLMaleSlike1 { get => URLMaleSlike; set => URLMaleSlike = value; }
public void DodajRecenziju(string tekstRecenzije, double ocjenaArtikla)
{
recenzije.Add(new Recenzija(tekstRecenzije, OcjenaArtikla));
IzracunajOcjenu();
}
void IzracunajOcjenu()
{
double suma = 0.0;
foreach (Recenzija recenzija in recenzije)
{
suma += recenzija.OverallRating;
}
ocjenaArtikla = suma / recenzije.Count;
}
}
}
Tip.cs：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
namespace BestDeal.Models
{
//klasa koja omogucava dodavanje tipova
public class Tip
{
public Tip()
{
}
//TODO:Moguce opcije nekog IDa ili liste specificnih polja koju ima svaki tip (radi razlicitih detalja kod recenzija i sl.)
public Tip(string ime)
{
Ime = ime;
}
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int idTipa { get; set; }
public string Ime { get; set; }
public override bool Equals(object obj)
{
var other = obj as Tip;
if (other == null)
{
return false;
}
return other == this;
}
public override int GetHashCode()
{
return HashCode.Combine(idTipa);
}
public static bool operator ==(Tip Tip1, Tip Tip2)
{
if (Object.ReferenceEquals(Tip1, null) && Object.ReferenceEquals(Tip2, null))
return true;
if (Object.ReferenceEquals(Tip1, null) || Object.ReferenceEquals(Tip2, null))
return false;
return Tip1.Ime == Tip2.Ime;
}
public static bool operator !=(Tip Tip1, Tip Tip2)
{
return !(Tip1 == Tip2);
}
}
}
我希望可以进行种子操作，并且能够将数据库条目成功迁移回Azure。如果存在这样的可能性，我会敞开心for。
答案 0 :(得分：2)
您正在尝试使用具有以下特定要求的EF Core Model seed data：
要添加具有关系的实体，需要指定外键值
和
如果实体类型在阴影状态下具有任何属性，则可以使用匿名类提供值
很快，您不能将导航属性用于这种类型的数据播种。
您的情况是什么意思
TipArtikla = ParoviTip["Laptopi"],
没有效果。
，您需要：
Tip的{{1}}和Artikal实体 。对于HasData，可以在模型中添加显式的FK属性，或者使用匿名类型（由于缺乏编译时间支持，这可能很烦人并且容易出错）。在这两种情况下，上一行都应该变成
Arktical