Can't update Composite data with wcf ria servics

Question

Suppose I have entity MyTab which has composite property MyList. WCF generates code fors MyTab for update like:

public void UpdateMyTab(MyTab currentMyTab) 
{          
    this.ObjectContext.MyTabs
                      .AttachAsModified(currentMyTab, 
                                        this.ChangeSet.GetOriginal(currentMyTab));
}

When only composite data changed, MyTab data not changed, then submit changes, I will get error "Value cannot be null.\r\nParameter name: original." because no orginal for MyTab. changeset will have 2 item: MyTab and MyList.

How to resolve this problem?

Answer 1

You should check first the return value of GetOriginal if its null, before callling AttachAsModified. If GetOriginal returns null you should Attach the entity only to the ObjectContext. I don´t tested it but i would update your method to the following.

public void UpdateMyTab(MyTab currentMyTab) {          
  var original = this.ChangeSet.GetOriginal(currentMyTab);

  if (original != null) {
    this.ObjectContext.MyTabs.AttachAsModified(currentMyTab, original);
  }
  else {
    this.ObjectContext.MyTabs.Attach(currentMyTab);
  }
}