我有以下实体类：
namespace Entities
{
public abstract class EntityBase
{
public EntityBase()
{
Id = Guid.NewGuid();
}
public Guid Id { get; set; }
}
}
public class Name : EntityBase
{
public DateTime LastUpdatedTime { get; set; }
public string Name { get; set; }
public Package Package { get; set; }
}
public class Owner : EntityBase
{
public DateTime LastUpdatedTime { get; set; }
public Guid ObjectId { get; set; }
public List<Package> Packages { get; set; }
}
public class Status : EntityBase
{
public string Name { get; set; }
public int SortPriority { get; set; }
}
public class Package : EntityBase
{
public Package()
{
}
public Guid? RequestorId { get; set; }
public string Requestor { get; set; }
public Name Name { get; set; }
public List<Owner> Owners { get; set; }
public Status StatusDetails { get; set; }
}
我有以下模型类：
namespace Models
{
public abstract class ModelBase
{
public Guid Id { get; set; }
}
}
public class Name : ModelBase
{
public DateTime LastUpdatedTime { get; set; }
public string Name { get; set; }
public Package Package { get; set; }
}
public class Owner : ModelBase
{
public DateTime LastUpdatedTime { get; set; }
public Guid ObjectId { get; set; }
public List<Package> Packages { get; set; }
}
public class Status : ModelBase
{
public string Name { get; set; }
public int SortPriority { get; set; }
}
public class Package : ModelBase
{
public Package()
{
}
public Guid? RequestorId { get; set; }
public string Requestor { get; set; }
public Name Name { get; set; }
public List<Owner> Owners { get; set; }
public Status StatusDetails { get; set; }
}
这是 DbContext 类：
using Entities;
public class WriteContext : DbContext
{
public DbSet<Package> Packages { get; set; } = null!;
public DbSet<Name> Names { get; set; }
public DbSet<Owner> Owners { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Package>().Property(t => t.Id)
.ValueGeneratedOnAdd()
.HasDefaultValueSql("NEWSEQUENTIALID()");
modelBuilder.Entity<Package>()
.HasOne(s => s.StatusDetails)
.WithOne()
.HasForeignKey<Package>(x => x.Status)
.HasPrincipalKey<Status>(x => x.Name)
.IsRequired(false)
.OnDelete(DeleteBehavior.NoAction);
modelBuilder.Entity<Status>()
.ToTable("Statuses");
modelBuilder.Entity<JobNotification>().Property(t => t.Id)
modelBuilder.Entity<Package>()
.HasOne(package => package.Name)
.WithOne(name => name.Package)
.HasForeignKey<Name>(name => name.Id);
modelBuilder.Entity<Package>()
.HasMany(package => package.Owners)
.WithMany(owner => owner.Packages);
modelBuilder.Entity<Owner>().Property(owner => owner.Id)
.ValueGeneratedOnAdd()
.HasDefaultValueSql("NEWSEQUENTIALID()");
modelBuilder.Entity<Owner>()
.HasIndex(owner => owner.ObjectId);
modelBuilder.Entity<Name>()
.HasIndex(name => name.Name);
}
public WrietContext(DbContextOptions<WriteContext> options)
: base(options)
{
}
}
这是存储库类：
using Models;
public class DatabasePackagesRepository : RepositoryBase<Entities.Package, Models.Package>, IDatabasePackagesRepository
{
private readonly WriteContext _writeContext;
public DatabasePackagesRepository(WriteContext writeContext)
: base(writeContext)
{
_readContext = readContext;
}
public override Entities.Package MapModelToEntity(Models.Package model)
{
return new Entities.Package
{
Id = model.Id,
RequestorId = model.RequestorId,
Requestor = model.Requestor
};
}
public override Models.Package MapEntityToModel(Entities.Package entity)
{
return new Models.Package
{
Id = entity.Id,
RequestorId = entity.RequestorId,
Requestor = entity.Requestor
};
}
public async Task<List<Models.Package>> GetPackagesAsync()
{
var entities = await _readContext.Packages.ToListAsync();
return entities.Select(MapEntityToModel).ToList();
}
运行此程序时，我看到错误
System.InvalidOperationException：LINQ 表达式 'DbSet() .Where(s => DatabasePackagesRepository.MapEntityToModel(s).Owners .Any(o => o.ObjectId == __Parse_0))' 无法翻译。以可翻译的形式重写查询，或者通过插入对“AsEnumerable”、“AsAsyncEnumerable”、“ToList”或“ToListAsync”的调用来显式切换到客户端评估。
如何更新 MapEntityToModel 以包含所有者、名称和状态详细信息？
快速回答：使用已经支持 EF
IQueryable例如使用 Automapper：
public async Task<List<Models.Package>> GetPackagesAsync()
{
var config = new MapperConfiguration(cfg => cfg.CreateMap<Entities.Package, Models.Package>());
var models = await _readContext.Packages
.ProjectTo<Entities.Package>(config)
.ToListAsync();
return models;
}
我强烈建议避免像这样的通用存储库模式。将 EF 抽象到这种程度会导致代码效率极低，从而导致难以使用、速度缓慢和内存使用过多。当存储库返回适合所有场合而不是实体的“模型”时，您最终得到的模型是它们映射到的实体的严格一对一副本。既然如此，他们的目的是什么？？
视图模型绝对有一个目的，但它们包含的内容应该完全由视图或其消费者的需求决定。通常，这些是实体和相关数据的简化视图或“扁平化”表示。存储库的工作不是为这些视图模型提供服务，它应该只是实体的一个薄包装器，以提供一个简单的抽象点作为单元测试的边界，或者确保执行核心查询规则。
通用存储库的主要问题，无论它们返回实体还是视图模型，都使得支持高效查询变得非常困难和/或复杂。想想你需要做什么来支持：
EF 及其
IQueryable