在EF Core 2.0中,我们能够从IEntityTypeConfiguration
派生出更清晰的Fluent API映射(source)。
如何扩展此模式以使用基础实体?在下面的例子中,我怎么能有一个BaseEntityConfiguration
来减少LanguageConfiguration
和MaintainerConfiguration
中的重复,只修改BaseEntity
中的BaseEntityConfiguration
中的属性?这样的BaseEntityConfiguration
会是什么样子;如果有的话,如何在OnModelCreating()
中使用它?请参阅示例末尾附近的TODO代码。
例:
public abstract class BaseEntity
{
public long Id { get; set; }
public DateTime CreatedDateUtc { get; set; }
public DateTime? ModifiedDateUtc { get; set; }
}
public class Language : BaseEntity
{
public string Iso6392 { get; set; }
public string LocalName { get; set; }
public string Name { get; set; }
}
public class Maintainer : BaseEntity
{
public string Email { get; set; }
public string Name { get; set; }
}
public class FilterListsDbContext : DbContext
{
public FilterListsDbContext(DbContextOptions options) : base(options)
{
}
public DbSet<Language> Languages { get; set; }
public DbSet<Maintainer> Maintainers { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
//TODO: Possibly add something like BaseEntityConfiguration?
modelBuilder.ApplyConfiguration(new LanguageConfiguration());
modelBuilder.ApplyConfiguration(new MaintainerConfiguration());
}
}
public class LanguageConfiguration : IEntityTypeConfiguration<Language>
{
public void Configure(EntityTypeBuilder<Language> entityTypeBuilder)
{
//TODO: Move this to something like BaseEntityConfiguration?
entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
}
}
public class MaintainerConfiguration : IEntityTypeConfiguration<Maintainer>
{
public void Configure(EntityTypeBuilder<Maintainer> entityTypeBuilder)
{
//TODO: Move this to something like BaseEntityConfiguration?
entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
}
}
这样的东西可以工作(未经测试)?
public abstract class BaseEntityTypeConfiguration<TBase> : IEntityTypeConfiguration<TBase>
where TBase : BaseEntity
{
public virtual void Configure(EntityTypeBuilder<TBase> entityTypeBuilder)
{
//Base Configuration
}
}
public class MaintainerConfiguration : BaseEntityTypeConfiguration<Maintainer>
{
public override void Configure(EntityTypeBuilder<Maintainer> entityTypeBuilder)
{
entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
base.Configure(entityTypeBuilder);
}
}
另一种方法,如果您不想重复从同一基本实体继承的所有模型的列定义,如下所示:
protected override void OnModelCreating(ModelBuilder modelBuilder){
modelBuilder.Entity<Order>()
.Property(b => b.CreatedDateTime)
.HasDefaultValueSql("CURRENT_TIMESTAMP ");
modelBuilder.Entity<Adress>()
.Property(b => b.CreatedDateTime)
.HasDefaultValueSql("CURRENT_TIMESTAMP ");
// …
}
是找到从基本实体继承的所有实体,循环它们并调用如下所示的通用方法,其中放置了冗余逻辑:
protected override void OnModelCreating(ModelBuilder modelBuilder){
foreach (Type type in GetEntityTypes(typeof(BaseEntity))){
var method = SetGlobalQueryMethod.MakeGenericMethod(type);
method.Invoke(this, new object[] { modelBuilder });
}
}
static readonly MethodInfo SetGlobalQueryMethod = typeof(/*your*/Context)
.GetMethods(BindingFlags.Public | BindingFlags.Instance)
.Single(t => t.IsGenericMethod && t.Name == "SetGlobalQuery");
public void SetGlobalQuery<T>(ModelBuilder builder) where T : BaseEntity{
builder.Entity<T>().Property(o => o.CreatedDateTime).HasDefaultValueSql("CURRENT_TIMESTAMP");
// Additional Statements
}
对于“GetEntityTypes”方法,您需要Nuget包“Microsoft.Extensions.DependencyModel”
private static IList<Type> _entityTypeCache;
private static IList<Type> GetEntityTypes(Type type)
{
if (_entityTypeCache != null && _entityTypeCache.First().BaseType == type)
{
return _entityTypeCache.ToList();
}
_entityTypeCache = (from a in GetReferencingAssemblies()
from t in a.DefinedTypes
where t.BaseType == type
select t.AsType()).ToList();
return _entityTypeCache;
}
private static IEnumerable<Assembly> GetReferencingAssemblies()
{
var assemblies = new List<Assembly>();
var dependencies = DependencyContext.Default.RuntimeLibraries;
foreach (var library in dependencies)
{
try
{
var assembly = Assembly.Load(new AssemblyName(library.Name));
assemblies.Add(assembly);
}
catch (FileNotFoundException)
{ }
}
return assemblies;
}
在我看来它有点hacky,但对我来说工作正常!
有更多细节的来源: