What this post is all about is the following program written in C# using Entity Framework 6.1.3 throwing at line 25 and not at line 23. <\/p>\n
We can see the simplest usage of Entity framework here. There is a I create an entity object, save it into database and then I retrieve it at line 21. Because the class uses virtual properties, Entity Framework dynamically creates some custom type in order to be able to implement lazy behavior underneath.<\/p>\n Now let’s suppose I have a need to modify something in an object retrieved from a database. It turns out I can modify I actually have been trapped by this when I was in need of modifying some collection in complicated object graph. I am deeply disappointed the Entity Framework on one hand allows modification of non-virtual properties, but on the other hand it ignores virtual ones. This can make a developer run into a trouble. <\/p>\n Of course I am aware it is not good practice to work on objects of data model classes. I recovered myself from this situation with AutoMapper. But this is kind of a quirk, and a skilled developer has to hesitate to even try to modify something returned by Entity Framework.<\/p>\nTest<\/code> class and a TestChild<\/code> class which contains a reference to an instance of Test<\/code> named Parent<\/code>. This reference is marked as virtual<\/code> so that Entity Framework in instructed to load an instance in a lazy manner, i.e. upon first usage of that reference. In DDL model obviously TestId<\/code> column is a foreign key to Test<\/code> table. <\/p>\nValue<\/code> property, which is of pure string<\/code> type. What is more, I can also modify Parent<\/code> property, but… the modification is not preserved!<\/strong>. This program throws at line 25 because an assignment from line 24 is silently ignored by the framework.<\/p>\n