使LINQ扩展方法适用于我的类

Question

I have a Repository class, which as a method FromStore<TEntity> as below:

IQueryable<TEntity> FromStore<TEntity>() where TEntity : class;

Using this I can do things like:

MyRepository.FromStore<DatabaseModel>().SingleOrDefault(dm => dm.Id = Id);

Now, i'm thinking it's silly to make users of the class call FromStore when I could provide the SingleOrDefault method directly (you'd just have to specify the generic type parameter rather than it being inferred as is normally the case).

So, I wrote a method as below:

public TEntity SingleOrDefault<TEntity>(Expression<Func<TEntity, bool>> filter) where TEntity : class
{
    return FromStore<TEntity>().SingleOrDefault(filter);
}

Great! Now I can do this:

MyRepository.SingleOrDefault<DatabaseModel>(dm => dm.Id = Id);

However, I want to do the same for all the linq extension methods.
The only way I can think to do it currently is to create similar wrapper methods on my class for every single linq method.

This seems silly, surely there's a better way?

I was thinking could I somehow have my Repository class inherit the class that the linq extension methods extend, but they extend IQueriable<T> . My class doesn't implement that, because there's not just one T in the repository.

---

Can I get the linq extension methods to apply to my class somehow, even though I can't implement IQueryable<T> for a specific T ?

Answer 1

You could implement it as an extension method for your repository interface.

public static class RepositoryExtensions
{
    public static TEntity SingleOrDefault<TEntity>(
        this IRepository repository,
        Expression<Func<TEntity, bool>> filter
    )
    {
        return repository.FromStore<TEntity>().SingleOrDefault(filter);
    }
}