Entity Framework 6 Generic Eager Loading Query Method - entity-framework

Question

I am writing a generic querying method in Entity Framework 6, based off of this helpful article. Here's how it looks:
public static T QueryEagerLoad<T>(Expression<Func<T, bool>> match) where T : class
{
using (var databaseContext = new ClearspanDatabaseContext())
{
databaseContext.Configuration.LazyLoadingEnabled = false;
T retrievedObject = databaseContext.Set<T>().SingleOrDefault(match);
return retrievedObject;
}
}
I'm attempting to eagerly load any related entities, so I include disable to configuration variable LazyLoadingEnabled. While it loads the object, it does not load the related entities, per my view in the debugger. Why would this be? Am I missing something? I should note that I'm using Npgsql. Thanks in advance.

Answer 1

See Mikael Östberg's answer to this question. To use a generic method for querying with eager loading, it seems necessary to inject the includes. Here's how the generic method shaped up:
public static T Query<T>(Expression<Func<T, bool>> match, List<Expression<Func<T, object>>> includes) where T : class
{
using (var databaseContext = new ClearspanDatabaseContext())
{
var dataSet = databaseContext.Set<T>(); // Get the relevant DataSet
T retrievedObject = includes.Aggregate( // Eagerly load the passed navigation properties
dataSet.AsQueryable(),
(current, include) => current.Include(include)
).SingleOrDefault(match); // Find exactly one or zero matches
return retrievedObject;
}
}
And an example of a call that injects the properties to eagerly load (the includes parameter in the generic method above):
public static Lumber GetLumber(int databaseId)
{
Expression<Func<Lumber, object>> lengthProperty = (lumber => lumber.Length);
Expression<Func<Lumber, object>> thicknessProperty = (lumber => lumber.Thickness);
Expression<Func<Lumber, object>> widthProperty = (lumber => lumber.Width);
List<Expression<Func<Lumber, object>>> lumberNaviationProperties = new List<Expression<Func<Lumber, object>>>() { lengthProperty, thicknessProperty, widthProperty };
Lumber retrievedLumber = DatabaseOperations.Query<Lumber>((lumber => lumber.DatabaseId == databaseId), lumberNaviationProperties);
return retrievedLumber;
}