Question

i have two simple models that have one-many relation

public class X{
  public int id {get;set;}
  public virtual Y y{ get; set; }
  public string description{get;set;}
}
public class Y{
  public int id{get;set;}
  public string name{get;set;}
}

and from the entity framework i set the relation

I’m trying to submit a form that creates a new X record with existing Y value

the returned data from the form to the action is the string description and y_id.

on the action when i try to specify the object from the parameters

public ActionResult sth(X x){}

the x.y is set to null (which is expected…) while when i tried the following …

x.y = (from i in Y where i.id == that_id select i).first(); 
...
db.saveChanges();

the entity framework inserted a new Y record to the database …

i know that i’m doing something wrong … your help will be very appreciated !

Answer 1

It seems an issue with tracking Y objects in the dbContext. how are you generating the collection Y you querying with linq? do you fetch it from the database using a dbContext? or from some other source?

if not, you need to be fetching it using a context or using the Attach() function so it could be properly tracked.

Another question pops up. how come a new Y is inserted? Don’t you have a primary key defined in the database? or is it try to insert then an exception is thrown?

These are my thoughts on the matter.