Question

I have this class (you can see it in its entirety here)…

internal class BaseRepository<I, C> : IRepository<I>
    where I : class, IBaseObject
    where C : BaseObject
{
    private Context _context;

    public IEnumerable<I> FindBy(Expression<Func<I, bool>> predicate)
    {
        return _context.Set<C>().ToList().Cast<I>().AsQueryable().Where(predicate);
    }

    // other methods.
}

How can I work this so I don’t have to call .ToList() which I believe causes EF to return everything in .Set<C>()

Using this without .ToList() and .AsQueryable() causes the error:

System.NotSupportedException: Unable to cast the type ‘Sln.DAL.Sql.Entities.Project’ to type ‘Sln.DAL.Entities.IProject’. LINQ to Entities only supports casting EDM primitive or enumeration types.

Answer 1

If we add a constraint

internal class BaseRepository<I, C> : IRepository<I>
    where I : class, IBaseObject
    where C : BaseObject, I

Can we then use

_context.Set<C>().Where(predicate).AsEnumerable();