Entity Framework 4 selective lazy loading properties

Question

Is it possible to load an entity excluding some properties? One of this entity\'s properties is expensive to select. I would like to lazy load this property. Is that possibl

Answer 1

Given a query over an EntityFramework DbSet, where the targeted entity contains a BigProperty and a SmallProperty, When you're trying to only access the SmallProperty without loading the BigProperty in memory :

//this query loads the entire entity returned by FirstOrDefault() in memory
//the execution is deferred during Where; the execution happens at FirstOrDefault
db.BigEntities.Where(filter).FirstOrDefault()?.SmallProperty;

//this query only loads the SmallProperty in memory
//the execution is still deferred during Select; the execution happens at FirstOrDefault
//a subset of properties can be selected from the entity, and only those will be loaded in memory
db.BigEntities.Where(filter).Select(e=>e.SmallProperty).FirstOrDefault();

Therefore you could exploit this behaviour to only query the BigProperty where you actually need it, and use select statements to explicitly filter it out everywhere else.

I tested this with the Memory Usage functionality from the Visual Studio debug Diagnostic Tools.