Linq to SQL Foreign Keys & Collections

Question

I'm a still trying to wrap myself around LINQ to SQL and foreign key relationships.

I have a table called "Parent" and another called "Children". I have a OneToMany relationship, where a Parent can have multiple Children. My DBML looks something like:

<Table Name="" Member="Parents">
<Type Name="Parent">
  <Column Member="ParentID" Type="System.String" IsPrimaryKey="true" CanBeNull="false" />
  <Column Member="ChildID" Type="System.String" CanBeNull="false" />
  <Association Name="Parent_Child" Member="Childs" ThisKey="ParentID" OtherKey="ParentID" Type="Child" />
</Type>
</Table>
<Table Name="" Member="Childs">
<Type Name="Child">
  <Column Member="ChildID" Type="System.String" IsPrimaryKey="true" CanBeNull="false" />
  <Column Member="ParentID" Type="System.String" CanBeNull="false" />
  <Association Name="Parent_Child" Member="Parent" ThisKey="ParentID" OtherKey="ParentID" Type="Parent" IsForeignKey="true" />
</Type>
</Table>

In my code, I would like do to something like:

// parent has already been loaded from the datacontext
parent.Childs = <some collection of children>
db.SubmitChanges();

But when I do that I get the following error:

A member defining the identity of the object cannot be changed. Consider adding a new object with new identity and deleting the existing one instead.

Can anyone tell me how to properly accomplish this?

Were the child records retrieved using the same data context or a different one? — Randy Minder

slash shogdhe slash shogdhe · Accepted Answer · 2010-12-23T20:40:38

this is actually the error of datacontext,i think u have multiple instance of datacontext.. well u can not add any entity in datacontext witch is already fetched through another instance of datacontext... even u can so it by setting datacontext.objecttrackingenabled to false and then u can add it to another data context then it will work for sure....

Linq to SQL Foreign Keys & Collections

1 Answers