Question

i think this is the first time i’ve not been able to find the answer to my question just by searching.

I’m doing some prototypes for a remake of our company system and i hit upon a problem i can’t seem to get my head around.

I’m trying to utilise a reasonably generic DAO coupled dependency injection.
The problem i’m having is that i’d like to use a third party library for query definition within the method of the interface.

An example

public interface TestDAO<TEntity>
{
    /// <summary>
    /// get ALL the things
    /// </summary>
    /// <returns></returns>
    IEnumerable<TEntity> GetAll();

    /// <summary>
    /// Runs a supplied "where" clause and returns ALL the matched results
    /// </summary>
    IEnumerable<TEntity> FindAll(Specification<TEntity> specification);
}

Specification in this case is an object from a third party library called LinqSpecs.

It is my understanding that by doing this i’m essentially forcing a dependency on the third-party library on any implementation of the interface.

I understand that I can just forego using the library but if possible i’d like to keep it, at least until we’ve assessed its usefulness.

My question is, is there a way of doing this(or something similar) without dragging the third party dependency with it.

Thanks in advance.

Answer 1

You actitually want to give your interface TestDAO a searchfilter that can be hidden behind your own interface

    public interface TestDAO<TEntity>
    {
        IEnumerable<TEntity> FindAll(ISearchFilter<TEntity> specification);
    }

    public interface ISearchFilter<TEntity>
    {
    }

The searchfilter implementation contains the actual data

    public class LinqSpecsSearchFilter : ISearchFilter<TEntity>
    {
        Specification<TEntity> specification;
    }

The downside of this aproach is that
your TestDAO implementation must do some ugly casting to get the LinqSpecs.Specification