我尝试使用以下代码获取 IEntityModelBuilder 的所有实现,但它返回一个空集合。
public class EntityFrameworkDbContext : DbContext
{
//constructor(s) and entities DbSets...
private static IEnumerable<IEntityModelBuilder<IEntity>> _entitymodelBuilders;
internal IEnumerable<IEntityModelBuilder<IEntity>> EntityModelBuilders
{
get
{
if (_entitymodelBuilders == null)
{
var type = typeof(IEntityModelBuilder<IEntity>);
_entitymodelBuilders = Assembly.GetAssembly(type).GetTypes()
.Where(t => type.IsAssignableFrom(t) && t.IsClass)
.Select(t => (IEntityModelBuilder<IEntity>)Activator.CreateInstance(t, new object[0]));
}
return _entitymodelBuilders;
}
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
foreach (var builder in EntityModelBuilders)
builder.Build(modelBuilder);
base.OnModelCreating(modelBuilder);
}
}
internal interface IEntityModelBuilder<TEntity> where TEntity : IEntity
{
void Build(DbModelBuilder modelBuilder);
}
//sample implementation
internal class UserModelBuilder : IEntityModelBuilder<User>
{
public void Build(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<User>()
.ToTable("users")
.HasKey(e => e.Id);
modelBuilder.Entity<User>()
.Property(e => e.Id)
.HasColumnName("id");
modelBuilder.Entity<User>()
.Property(e => e.Email)
.HasColumnName("email");
//and so on...
}
}
如果我用
改变类型var type = typeof(IEntityModelBuilder<User>);
类型获取代码运行良好并返回预期的 UserModelBuilder。我如何使用泛型来做到这一点?
最佳答案
尽管 Slava 的解决方案有效,但由于 Contains
,它通常不是完全安全的. 有可能某些其他接口(interface)/类型可能包含您要搜索的接口(interface)的名称。在这种情况下,假设您有另一个名为 IEntityModelBuilderHelper
的接口(interface).
此外,只需很少的努力,您就可以将这段代码概括为更加强大。考虑以下两种方法:
public static IEnumerable<Type> GetAllTypes(Type genericType)
{
if (!genericType.IsGenericTypeDefinition)
throw new ArgumentException("Specified type must be a generic type definition.", nameof(genericType));
return Assembly.GetExecutingAssembly()
.GetTypes()
.Where(t => t.GetInterfaces()
.Any(i => i.IsGenericType &&
i.GetGenericTypeDefinition().Equals(genericType)));
}
还有,
public static IEnumerable<Type> GetAllTypes(Type genericType, params Type[] genericParameterTypes)
{
if (!genericType.IsGenericTypeDefinition)
throw new ArgumentException("Specified type must be a generic type definition.", nameof(genericType));
return Assembly.GetExecutingAssembly()
.GetTypes()
.Where(t => t.GetInterfaces()
.Any(i => i.IsGenericType &&
i.GetGenericTypeDefinition().Equals(genericType) &&
i.GetGenericArguments().Count() == genericParameterTypes.Length &&
i.GetGenericArguments().Zip(genericParameterTypes,
(f, s) => s.IsAssignableFrom(f))
.All(z => z)));
}
前者将为您提供实现所提供的通用类型定义 的所有类型,即typeof(MyGenericType<>)
,对泛型类型参数没有任何限制。后者将执行相同的操作,但具有提供的类型约束。
考虑以下类型:
public interface IFoo<T> { }
public interface IEntity { }
public class A : IEntity { }
public class Foo : IFoo<IEntity> { }
public class FooA : IFoo<A> { }
public class FooS : IFoo<string> { }
var types = GetAllTypes(typeof(IFoo<>));
将返回 3 种类型:{ Foo, FooA, FooS }
同时 var types = GetAllTypes(typeof(IFoo<>), typeof(IEntity));
将只返回两种类型:{ Foo, FooA }
.
关于c# - 获取通用接口(interface)的所有实现类型,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/42245011/