Fetch vs FetchMany in NHibernate Linq provider

Question

NHibernate eager loading can be done using Fetch and FetchMany, as described in NHibernate Linq Eager Fetching on Mike Hadlow's blog.

What is the difference between these two methods and under what circumstance would each be used?

Diego Mijelshon · Accepted Answer · 2010-12-09 13:00:34Z

107

Fetch should be used for references and FetchMany for collections.

This is particularly important because only FetchMany can be combined with ThenFetchMany to fetch "grandchildren" collections.

Example:

session.Query<User>() .FetchMany(u => u.Orders) .ThenFetchMany(o => o.OrderItems)

answered Dec 9, 2010 at 13:00

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3 Comments

Is there a problem using Fetch() on collections if you're not planning on calling ThenFetch() afterwards?

@Diego Mijelshon since both Fetch and FetchMany work, what is the difference?

@hardywang: the way they can be chained to fetch more levels. Just look at the method signatures.