[英]EntityFramework Code First FluentAPI TPC
這是我的域實體 :
public class Province
{
private ICollection<City> _cities;
public virtual ICollection<City> Cities
{
get { return _cities ?? (_cities = new HashSet<City>()); }
set { _cities = value; }
}
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual double Latitude { get; set; }
public virtual double Longitude { get; set; }
}
public class City
{
private Province _province;
public virtual Province Province
{
get { return _province ?? (_province = new Province()); }
set { _province = value; }
}
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual string Latitude { get; set; }
public virtual string Longitude { get; set; }
}
映射 :
public class ProvinceMap : EntityTypeConfiguration<Province>
{
public ProvinceMap()
{
this.ToTable("Province");
this.HasKey(p => p.Id);
this.Property(x => x.Id).HasColumnName("Id");
this.Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
this.Property(x => x.Name).HasMaxLength(50).IsRequired();
this.Property(x => x.Latitude).IsRequired();
this.Property(x => x.Longitude).IsRequired();
//this.HasMany(x => x.Cities)
// .WithRequired(x => x.Province)
// .HasForeignKey(x => x.Id);
}
}
public class CityMap : EntityTypeConfiguration<City>
{
public CityMap()
{
this.ToTable("City");
this.HasKey(x => x.Id);
this.Property(x => x.Id).HasColumnName("Id");
this.Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
this.Property(x => x.Name).HasMaxLength(50).IsRequired();
this.Property(x => x.Latitude).IsRequired();
this.Property(x => x.Longitude).IsRequired();
this.HasRequired(x => x.Province)
.WithMany(x => x.Cities)
.HasForeignKey(x => x.Id);
}
}
內容 :
public class DataContext : DbContext
{
public DataContext(): base("DataContext")
{
Database.SetInitializer(new MigrateDatabaseToLatestVersion<DataContext, Configuration>("DataContext"));
}
public DbSet<Province> Provinces { get; set; }
public DbSet<City> Cities { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new ProvinceMap());
modelBuilder.Configurations.Add(new CityMap());
//base.OnModelCreating(modelBuilder);
}
}
在Nuget軟件包控制台上運行“ update-database”命令時,出現錯誤:
連接“ City_Province”中的元素角色“ City_Province_Source”中的無效多重性。 因為從屬角色是指關鍵屬性,所以多重性屬性從屬角色的上限必須等於“ 1”。
從邏輯上講,您正在嘗試定義一對多關系。 因為City
不能在許多Provinces
,一個Province
可以有許多Cities
。
在這種情況下,您不必在映射中指定HasRequired
和WithMany
。
從CityMap
刪除以下代碼
this.HasRequired(x => x.Province)
.WithMany(x => x.Cities)
.HasForeignKey(x => x.Id);
在Province
表中具有ICollection<City>
,在City
表中具有Province
的屬性類型足以建立關系。
輸出將是這樣。
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