How to attach an object that contains a relation of n to n?

Question

I have two tables that are nn related. And I have a method that takes one object and saves.

 public int Save(Table1 element) { using (var database = new Entities()) { if (element.ID == 0) { database.Table1.AddObject(element); } else { database.Attach(element); // database.ObjectStateManager.GetObjectStateEntry(element).SetModified(); database.Refresh(RefreshMode.ClientWins, element); } return database.SaveChanges(); } } 

When I do not try to change obj1.Table2 , it automatically joins and saves. But if I try to change this EntityCollection

 element.Table2.Add(tb2); 

And save, I get the following error:

An object with a temporary EntityKey value cannot be bound to the object context.

in line: database.Attach(element);

How can i fix this?

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Database:

 Table 1 Table 2 ID | Name ID | Name --------- ------------------- 1 | One 1 | Related to One 2 | Two 2 | Related to One 3 | Three Table 3 Tb1 | Tb2 --------- // 1 | 1 // 1 | 2 

Creating the Table1 object:

 var element = GetTable1Obj(1); element.Table2.Add(GetTable2Obj(1)); // GetTable2Obj uses a separated context element.Table2.Add(GetTable2Obj(2)); // like Save method to return the object provider.Save(element); // Method above 

Answer 1

If your working Entity frame model is set something like this, you should be able to change t1 or t2 without any problems. while maintaining

From the look of table 3 in your example, you don't have a key for the entries. This will cause problems when modifying an Entity object. Which DB Fk you have installed.