【发布时间】：2020-02-10 16:48:56
【问题描述】：
我正在尝试创建一个强类型的Id 类，它现在在内部拥有“long”。下面实现。
我在实体中使用它的问题是 Entity Framework 给了我一条消息，即属性 Id 已经映射到它上面。请参阅下面的IEntityTypeConfiguration。
注意：我的目标不是严格执行 DDD。所以请在评论或回答时记住这一点。输入 Id 背后的整个 id 是为进入项目的开发人员准备的，他们强烈输入在所有实体中使用 Id，当然翻译为 long（或 BIGINT） - 但很明显其他人。
在类和配置之下，这是行不通的。 repo 可以在https://github.com/KodeFoxx/Kf.CleanArchitectureTemplate.NetCore31找到，
-
Id班级（现已注释掉）：https://github.com/KodeFoxx/Kf.CleanArchitectureTemplate.NetCore31/blob/master/Source/Common/Kf.CANetCore31/DomainDrivenDesign/Id.cs -
Entity和ValueObject类（对于Entity，属性Id的类型为Id.cs（上图）：https://github.com/KodeFoxx/Kf.CleanArchitectureTemplate.NetCore31/tree/master/Source/Common/Kf.CANetCore31/DomainDrivenDesign - 配置地址：https://github.com/KodeFoxx/Kf.CleanArchitectureTemplate.NetCore31/tree/master/Source/Infrastructure/Persistence/Kf.CANetCore31.Infrastructure.Persistence.Ef/EntityTypeConfigurations
Id 类实现（现在标记为已过时，因为在找到解决方案之前我放弃了这个想法）
namespace Kf.CANetCore31.DomainDrivenDesign
{
[DebuggerDisplay("{DebuggerDisplayString,nq}")]
[Obsolete]
public sealed class Id : ValueObject
{
public static implicit operator Id(long value)
=> new Id(value);
public static implicit operator long(Id value)
=> value.Value;
public static implicit operator Id(ulong value)
=> new Id((long)value);
public static implicit operator ulong(Id value)
=> (ulong)value.Value;
public static implicit operator Id(int value)
=> new Id(value);
public static Id Empty
=> new Id();
public static Id Create(long value)
=> new Id(value);
private Id(long id)
=> Value = id;
private Id()
: this(0)
{ }
public long Value { get; }
public override string DebuggerDisplayString
=> this.CreateDebugString(x => x.Value);
public override string ToString()
=> DebuggerDisplayString;
protected override IEnumerable<object> EquatableValues
=> new object[] { Value };
}
}
EntityTypeConfiguration 我使用的 ID 没有标记为实体 Person 的过时 不幸的是，当 Id 类型时，EfCore 不想映射它...当类型为 long 时没问题...其他拥有的类型，如您所见（Name）工作正常。
public sealed class PersonEntityTypeConfiguration
: IEntityTypeConfiguration<Person>
{
public void Configure(EntityTypeBuilder<Person> builder)
{
// this would be wrapped in either a base class or an extenion method on
// EntityTypeBuilder<TEntity> where TEntity : Entity
// to not repeated the code over each EntityTypeConfiguration
// but expanded here for clarity
builder
.HasKey(e => e.Id);
builder
.OwnsOne(
e => e.Id,
id => {
id.Property(e => e.Id)
.HasColumnName("firstName")
.UseIdentityColumn(1, 1)
.HasColumnType(SqlServerColumnTypes.Int64_BIGINT);
}
builder.OwnsOne(
e => e.Name,
name =>
{
name.Property(p => p.FirstName)
.HasColumnName("firstName")
.HasMaxLength(150);
name.Property(p => p.LastName)
.HasColumnName("lastName")
.HasMaxLength(150);
}
);
builder.Ignore(e => e.Number);
}
}
Entity 基类（当时我还在使用 Id，所以当它没有被标记为过时时）
namespace Kf.CANetCore31.DomainDrivenDesign
{
/// <summary>
/// Defines an entity.
/// </summary>
[DebuggerDisplay("{DebuggerDisplayString,nq}")]
public abstract class Entity
: IDebuggerDisplayString,
IEquatable<Entity>
{
public static bool operator ==(Entity a, Entity b)
{
if (ReferenceEquals(a, null) && ReferenceEquals(b, null))
return true;
if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
return false;
return a.Equals(b);
}
public static bool operator !=(Entity a, Entity b)
=> !(a == b);
protected Entity(Id id)
=> Id = id;
public Id Id { get; }
public override bool Equals(object @object)
{
if (@object == null) return false;
if (@object is Entity entity) return Equals(entity);
return false;
}
public bool Equals(Entity other)
{
if (other == null) return false;
if (ReferenceEquals(this, other)) return true;
if (GetType() != other.GetType()) return false;
return Id == other.Id;
}
public override int GetHashCode()
=> $"{GetType()}{Id}".GetHashCode();
public virtual string DebuggerDisplayString
=> this.CreateDebugString(x => x.Id);
public override string ToString()
=> DebuggerDisplayString;
}
}
Person（可以在https://github.com/KodeFoxx/Kf.CleanArchitectureTemplate.NetCore31/tree/master/Source/Core/Domain/Kf.CANetCore31.Core.Domain/People找到域和对其他值对象的引用）
namespace Kf.CANetCore31.Core.Domain.People
{
[DebuggerDisplay("{DebuggerDisplayString,nq}")]
public sealed class Person : Entity
{
public static Person Empty
=> new Person();
public static Person Create(Name name)
=> new Person(name);
public static Person Create(Id id, Name name)
=> new Person(id, name);
private Person(Id id, Name name)
: base(id)
=> Name = name;
private Person(Name name)
: this(Id.Empty, name)
{ }
private Person()
: this(Name.Empty)
{ }
public Number Number
=> Number.For(this);
public Name Name { get; }
public override string DebuggerDisplayString
=> this.CreateDebugString(x => x.Number.Value, x => x.Name);
}
}
【问题讨论】：
标签： c# entity-framework .net-core entity-framework-core domain-driven-design