C#中如何通过接口默认实现实现实体审计的自动调用

方案1：在基类BaseEntity中统一处理审计逻辑 #

既然所有实体都继承自BaseEntity，可以直接在基类构造函数中检查当前实例是否实现IAuditable，若实现则自动触发审计逻辑，从根源避免子类手动调用的遗漏问题。同时通过构造注入解决userNameProvider的依赖传递：

// 定义用户信息提供者接口
public interface IUserNameProvider
{
    Guid GetUserId();
}

// 修改基类逻辑
public abstract class BaseEntity
{
    public Guid Id { get; } = Guid.NewGuid();

    protected BaseEntity(IUserNameProvider userNameProvider)
    {
        if (this is IAuditable auditable)
        {
            auditable.CreatedBy = userNameProvider.GetUserId();
            auditable.Audit();
        }
    }
}

// 调整IAuditable接口，拆分职责
public interface IAuditable
{
    DateTime CreatedTime { get; set; }
    Guid CreatedBy { get; set; }

    void Audit()
    {
        CreatedTime = DateTime.UtcNow;
    }
}

// 子类只需继承+实现接口，无需手动处理审计
public class Car : BaseEntity, IAuditable
{
    public string Name { get; private set; }
    public DateTime CreatedTime { get; set; }
    public Guid CreatedBy { get; set; }

    public Car(string name, IUserNameProvider userNameProvider) 
        : base(userNameProvider)
    {
        Name = name;
    }
}

所有继承BaseEntity且实现IAuditable的实体，实例化时都会自动执行审计逻辑，无需子类编写额外代码，也避免了类型转换操作。

方案2：用泛型工厂封装实体创建逻辑 #

如果不想修改基类构造，可通过泛型工厂统一管理实体创建流程，确保审计逻辑被强制执行：

public interface IEntityFactory
{
    T Create<T>(Func<T> factoryMethod) where T : BaseEntity;
}

public class EntityFactory : IEntityFactory
{
    private readonly IUserNameProvider _userNameProvider;

    public EntityFactory(IUserNameProvider userNameProvider)
    {
        _userNameProvider = userNameProvider;
    }

    public T Create<T>(Func<T> factoryMethod) where T : BaseEntity
    {
        var entity = factoryMethod();
        
        if (entity is IAuditable auditable)
        {
            auditable.CreatedBy = _userNameProvider.GetUserId();
            auditable.Audit();
        }

        return entity;
    }
}

// 使用示例
var factory = new EntityFactory(new DefaultUserNameProvider()); // 替换为实际实现
var car = factory.Create(() => new Car("bmw"));

这种方式无需修改基类，所有实体创建都通过工厂完成，既能保证审计逻辑不遗漏，也可扩展其他公共创建逻辑。

额外优化：强化审计属性的安全性 #

可将CreatedTime和CreatedBy的外部访问权限设为只读，仅允许内部逻辑修改，避免外部随意篡改：

public interface IAuditable
{
    DateTime CreatedTime { get; }
    Guid CreatedBy { get; }

    void Audit(Guid createdBy)
    {
        (this as IAuditableInternal).CreatedTime = DateTime.UtcNow;
        (this as IAuditableInternal).CreatedBy = createdBy;
    }
}

// 内部接口用于属性设置
internal interface IAuditableInternal
{
    DateTime CreatedTime { get; set; }
    Guid CreatedBy { get; set; }
}

// 子类实现双接口
public class Car : BaseEntity, IAuditable, IAuditableInternal
{
    public string Name { get; private set; }
    DateTime IAuditable.CreatedTime { get; }
    Guid IAuditable.CreatedBy { get; }
    DateTime IAuditableInternal.CreatedTime { get; set; }
    Guid IAuditableInternal.CreatedBy { get; set; }

    public Car(string name, IUserNameProvider userNameProvider) 
        : base(userNameProvider)
    {
        Name = name;
    }
}

外部代码仅能读取审计属性，无法直接修改，保证审计数据的完整性。

内容的提问来源于stack exchange，提问作者Simon Great