Updating Child Entities, Possible Bug?

07-08-2009 11:58 AM |

Ok Guys,

I'm finally able to update child entities now if a make sure I have the proper CRUD operations for each entity in my datamodel and ONLY if I format my query's in a certain way it seems that you must use .First rather than .Single, Someone correct me if im doing soemthing wrong here but this is what finally got it working for just FYI for anyone who was having trouble with updating child entity's using the RIA framework and a DomainDataSource in this way. Thanks again to ColinBlaire and Theo67for your help with this.

Please look at the following code, is this possibly a bug? Anyone have any ideas on this?

The following code will update the child entity LU_TeamStatus using a).first:

Public Sub CancelTeam(ByVal current As tbl_TeamSchedule)
        If current.EntityState = EntityState.Detached Then
            Me.Context.Attach(current)
        End If

        Dim CancelTeam = (From a In Context.LU_TeamStatus _
                      Where a.TeamStatusID = 2 _
                      Select a).First

        current.LU_TeamStatus = CancelTeam
    End Sub

The following code will NOT update the child entity and just hangs when trying to update the child entity LU_TeamStatus using a).single

Public Sub CancelTeam(ByVal current As tbl_TeamSchedule)
        If current.EntityState = EntityState.Detached Then
            Me.Context.Attach(current)
        End If

        Dim CancelTeam = (From a In Context.LU_TeamStatus _
                      Where a.TeamStatusID = 2 _
                      Select a).Single

        current.LU_TeamStatus = CancelTeam
    End Sub

Re: Updating Child Entities, Possible Bug?

07-08-2009 12:14 PM |

The primary difference between .First and .Single is that .Single will throw an exception if there is not exactly one row in the results. Are you sure you don't have a duplicate row in LU_TeamStatus?

Re: Updating Child Entities, Possible Bug?

07-08-2009 12:21 PM |

Just double checked and "LU_TeamStatus" has all unique values.

Re: Updating Child Entities, Possible Bug?

07-08-2009 1:11 PM |

 Thanks Colin,

I think I already knew this one from working with webforms but it didnt click until just now. Try and catch returns the following exception:

The method 'Single' is not supported by LINQ to Entities. Consider using the method 'First' instead.

 I had forgotten that .Single was not supported. This was probably the issue the whole time, but the exception was not thrown until I put in the try & catch.