实体框架IValidatableObject参考DbContext [英] Entity Framework IValidatableObject reference DbContext

问题描述

我正在尝试使EF 4.1与存储库，UnitOfWork，将实体与EF分离以及进行验证有关.

I'm trying to get EF 4.1 working with Repository, UnitOfWork, separation of entities from EF and validation.

我遵循了此指南可以很好地将我的POCO实体与EF模型区分开来，我现在正在按照

I followed this guide to get a nice separation of my POCO entities from the EF model and I'm now following this guide to implement validation (with IValidatableObject).

我的解决方案包括:

• Contacts.Repository [引用EF和Contacts.Entities]:
  • Contacts.edmx
  • ContactsDbContext.cs
  • Contacts.Repository [references EF and Contacts.Entities]:
    • Contacts.edmx
    • ContactsDbContext.cs
    • Contact.cs(Contacts.Entities.Contact局部类)
    • Contact.cs(Contacts.Entities.Contact局部类)

    但是我正在通过验证碰到一堵砖墙:

    But I'm hitting a brick wall with the validation:

    1. 我无法向Contacts.Entities添加验证逻辑，因为这会导致对Contacts.Repository进行循环引用(contact.Validate(...)需要使用ContactsDbContext).因此，我创建了一个单独的Contacts.Validation项目.
    2. 但是，这意味着将Contact类分为部分类，以在Contacts.Entities和Contacts.Validation中定义Contact.该代码不再编译，因为您无法跨不同的程序集定义局部类.

    有人在这里给我指点吗?我已经在下面发布了代码...

    Anyone got any pointers for me here? I've posted the code below...

    Contacts.Repository.ContactsDbContext.cs:

    Contacts.Repository.ContactsDbContext.cs:

    namespace Contacts.Repository
    {
      public partial class ContactsDbContext : DbContext
      {
        public DbSet<Contact> Contacts { get; set; }
    
        protected override DbEntityValidationResult ValidateEntity(DbEntityEntry entityEntry, IDictionary<object, object> items)
        {
          items.Add("Context", this);
          return base.ValidateEntity(entityEntry, items);
        }
      }
    }
    

    Contacts.Entities.Contact.cs:

    Contacts.Entities.Contact.cs:

    namespace Contacts.Entities
    {
        public partial class Contact
        {
            public string Name { get; set; }
        }
    }
    

    Contacts.Validation.Contact.cs包含:

    Contacts.Validation.Contact.cs contains:

    namespace Contacts.Entities
    {
      public partial class Contact : IValidatableObject
      {
          public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
          {
              ContactsDbContext contacts = (ContactsDbContext)validationContext.Items["Context"];
    
              //Check if Contact already exists with the same Name
              if (contacts.Any<Contact>(c => c.Name == this.Name))
                yield return new ValidationResult("Contact 'Name' is already in use.", new string[] { "Name" });
    
              yield break;
          }
      }
    

    推荐答案

    技术上，您可以引入具有如下所示的显式实现的接口:

    Technically you could introduce an interface with an explicit implementation like so:

    在 Contacts.Entities 程序集中:

    public interface IContactsDbContext
    {
        IQueryable<Contact> Contacts { get; }
        // Not DbSet<Contact> because you don't want dependency on EF assembly 
    }
    
    //...
    
    public class Contact : IValidatableObject // No partial class anymore
    {
        public string Name { get; set; }
    
        public IEnumerable<ValidationResult> Validate(
            ValidationContext validationContext)
        {
            IContactsDbContext context = 
                validationContext.Items["Context"] as IContactsDbContext;
    
            if (context.Contacts.Any<Contact>(c => c.Name == this.Name))
                yield return new ValidationResult(
                    "Contact 'Name' is already in use.", new string[] { "Name" });
    
            yield break;
        }
        // IValidatableObject, ValidationResult and ValidationContext is in
        // System.ComponentModel.DataAnnotations.dll, so no dependency on EF
    }
    

    在 Contacts.Repository 程序集中(引用 Contacts.Entities 程序集):

    In Contacts.Repository assembly (references Contacts.Entities assembly):

    public class ContactsDbContext : DbContext, IContactsDbContext
    {
        public DbSet<Contact> Contacts { get; set; }
    
        IQueryable<Contact> IContactsDbContext.Contacts // explicit impl.
        {
            get { return Contacts; } // works because DbSet is an IQueryable
        }
    
        protected override DbEntityValidationResult ValidateEntity(
            DbEntityEntry entityEntry, IDictionary<object, object> items)
        {
            items.Add("Context", this);
            return base.ValidateEntity(entityEntry, items);
        }
    }
    

    可以删除

    Contacts.Validation 程序集.

    但是，我不太喜欢这种解决方案.通过Validate方法，您的POCO仍然依赖于存储库(无论是否存在接口).为了更好地分离关注点，我可能希望拥有一个单独的Validation类，该类也可能对存储库进行操作.或者，如果我要实现IValidatableObject，我可能只会进行仅依赖于模型对象属性的验证(例如生产日期一定不能晚于发货日期"之类的东西).好吧，这只是部分品味问题.您链接的第二个示例并不真正关心关注点的分离，因此您与第一个示例存在某种冲突.

    However, I do not really like this solution. Your POCO has - through the Validate method - still a dependency on the repository, if interface or not. For a stronger separation of concerns I would probably prefer to have a separate Validation class which does perhaps also operations on the repo. Or if I would implement IValidatableObject I would probably only do validations which depend on model object properties alone (things like "production date must not be later than shipping date" and so on). Well, it's partially a matter of taste. The second example you have linked does not really care about separation of concerns, so you have somehow a conflict with the first example.

    这篇关于实体框架IValidatableObject参考DbContext的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！