c# - 如何找到泛型类型派生自给定基类型的所有 DbSet？

Question

如何获取List包含类型派生自的所有 DbSet IncomingServiceOrderBase？

我可以使用反射来获取所有 DbSet，但是如何将其过滤到仅包含派生类型的那些？

语境

public class MyContext : DbContext
{
    public DbSet<BuildingOrder> BuildingOrders { get; set; }
    public DbSet<DeliveryOrder> DeliveryOrders { get; set; }
    public DbSet<RetailAssemblyOrder> RetailAssemblyOrders { get; set; }
}

模型

public class BuildingOrder : IncomingManufacturedProductOrderBase { }
public class DeliveryOrder : IncomingServiceOrderBase { }
public class RetailAssemblyOrder : IncomingServiceOrderBase { }

Answer 1

你可以这样做：

var sets =
    from p in typeof(MyContext).GetProperties()
    where p.PropertyType.IsGenericType
    && p.PropertyType.GetGenericTypeDefinition() == typeof(DbSet<>)
    let entityType = p.PropertyType.GetGenericArguments().First()
    where typeof(IncomingServiceOrderBase).IsAssignableFrom(entityType)
    select p.Name;

（这将返回属性的名称；如果您想要实际的 DbSet 实例，请替换p.Name为p.GetValue(context, null)）

Answer 2

typeof(BaseType).IsAssignableFrom(DerivedType). It'll return true/false. See http://msdn.microsoft.com/en-us/library/system.type.isassignablefrom.aspx

To turn DbSet<T> into T (so you can do this comparison) take each property's type and do something like this:

    public static Type GetGenericBaseType( this Type Type ) {
        if ( Type == null ) {
            throw new ArgumentNullException( "Type" );
        }
        if ( !Type.IsGenericType ) {
            throw new ArgumentOutOfRangeException( "Type", Type.FullName + " isn't Generic" );
        }
        Type[] args = Type.GetGenericArguments();
        if ( args.Length != 1 ) {
            throw new ArgumentOutOfRangeException( "Type", Type.FullName + " isn't a Generic type with one argument -- e.g. T<U>" );
        }
        return args[0];
    }