基于实体类型的通用存储库应用过滤器

Question

I have a generic repository:

 public class Repository<T> : IRepository<T> where T : class, IEntity
 {
    public List<T> GetAllList(Expression<Func<T, bool>> filter)
    {
        return GetQueryable().Where(filter).ToList();
    }

    private IQueryable<T> GetQueryable()
    {
        IQueryable<T> query = Context.Set<T>().AsQueryable();
        query = ApplyTagFilter(query)
        return query;
    }

    private IQueryable<T> ApplyTagFilter(IQueryable<T> query)
    {
       //if T is ITagableEntity filter by token somehow
       if(typeof(ITagableEntity).IsAssignableFrom(typeof(T)))
       {
          //does not work and looks ugly :(
          return (query as IQueryable<ITagableEntity>)
             .Where(q => q.tagtoken > 10) as IQueryable<T>;
       }
       else
       {
           return query;
       }
    }
 }

Some of my entities are tagable, ie implement ITagableEntity interface:

public interface ITagableEntity : IEntity
{
    int tagtoken { get; set; }
}

How can I implement if condition in ApplyTagFilter method ? What is the best way to approach it ? The way I tried does not work and looks ugly. Generic parameter T is of type IEntity, but ITagableEntities inherits from IEntity, thus I have to cast back and forth in order to apply the filter.

Any help would be greatly appreciated.

Answer 1

Maybe you really consider creating some specific repository for taggable entities.

But if you want to make this code work — you can use cast.

return query.Cast<ITagableEntity>()
                .Where(q => q.tagtoken > 10)
                .Cast<T>();

Answer 2

I solved the problem by implementing an idea proposed by FCin and VorobeY1326 . I marked GetQueryable() as protected virtual and overrode it in TagableRepository class.

public class TagableRepository<T> : Repository<T> where T : class, ITagableEntity
{
    protected override IQueryable<T> GetQueryable()
    {
        return base.GetQueryable().Where(q => q.tagtoken > 10);
    }
}