带有存储库模式的OData冲突

Question

I have method GetByID in my repository that return generic type:

 public T GetById(object id)
 {
    return this.Entities.Find(id);
 }

I'm going to use OData to filtering data, and for that (when I'm using $expand for single row) I need to something like:

SingleResult.Create(repository.GetByID(id));

But of course I got error, because for SingleResult needs type IQueryable<T> .

How can I implement it?

One bad solution is change my GetByID to:

public IQueryable<T> GetById(object id)
{
    return this.Entities.FirstOrDefault(p => p.ID == (int)id);
}

But I prefer to use T GetById because in my opinion it is more correct.

What type should return GetByID ? Could you please advise me what to do?

Answer 1

The IQueryable interface defers the filtering to the caller which can do further filtering before "rendering" the final list (in Entity Framework it means executing the actual query with all the WHERE parameters applied at once).

So SingleResult needs an IQueryable to add any further filtering.

If this.Entities is an EF collection (DBSet), you can use .Where(o => o.Id == id) which will return an IQueryable object.

Your question is more one of design if it is good practice to have the Repository class return an IQueryable. I would say it depends on the general design of your solution and which responsibility you assign to which layer.

By looking at this answer ( OData $expand, DTOs, and Entity Framework ), if ODataController is expecting a IQueryable return type for [Queryable] methods then it is perfectly fine for the repository to return an IQueryable.