How do you override lazy loading on a single LINQ query using Fluent NHibernate

Question

By default, I have lazy loading enabled on all my models, and that's the way I want to keep things. However, sometimes I want to eagerly fetch all the data up front on an individual query. From everything I've read, I should be using FetchMany() for this purpose. However, if I do:

var dbRecipe = (from r in session.Query<Models.Recipes>().FetchMany(x => x.Ingredients)
                where r.RecipeId == recipeId
                select r).FirstOrDefault();

Then dbRecipe.Ingredients.Count() returns 1. In other words, it only returns the first ingredient of that recipe. However, if I do:

var dbRecipe = (from r in session.Query<Models.Recipes>()
                where r.RecipeId == recipeId
                select r).FirstOrDefault();

Then dbRecipe.Ingredients.Count() returns 12, which is correct, however it performs a second query to load the ingredients for that recipe.

How do I make FetchMany fetch all 12 records up front? I was assuming that was the difference between Fetch and FetchMany. I'm clearly doing something wrong.

MichaC · Accepted Answer · 2013-12-24 22:38:53Z

2

You can work around this by not running FirstOrDefault as the last statement. This will cause nh to run a top(1) query which yields wrong results...

Instead use .ToList().FirstOrDefault().

Or you use QueryOver<> which works fine

session.QueryOver<Models.Recipes>()
   .Fetch(prop => prop.Ingredients)
   .Eager
   .Where(p => p.RecipeId == recipeId)
   .SingleOrDefault();

answered Dec 24, 2013 at 22:38

MichaC

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1 Comment

Mike Christensen Over a year ago

Works perfectly! (Ended up using the QueryOver<> method)

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