DataPortal.Delete succeeded?

gmclean posted on Wednesday, November 22, 2006

    It has been a while since I have worked on CSLA related projects so maybe I am missing something simple.

I want to use CSLA to delete a business object directly. In this BO I have defined an override for dataportal delete and it seems to work fine except for one thing. If all the data is deleted successfully I would like to pass back a boolean letting the calling program know the deletes were OK. I tried creating a public boolean property and setting it to true in the override of dataportal delete if all went well in the delete transaction. The property gets set but the value does not persist when I look at the BO in the calling program.

Any suggestions on a good way to let the calling program know the BO was deleted successfully?

Thanks for your help,

George

Q Johnson replied on Wednesday, November 22, 2006

You're clearly not going to get a return value all the way back from your DP_Delete routine and I don't see how you could pass a variable by reference in hopes of getting it back modified to suit, either.

So the only other option appears to be some sort of test to see if the persisted object still exists.  This shouldn't be hard should it?  Your calling routine must know the ID value of the object (else how could it have deleted it directly?).  So you can either (a) rely on logic you may already have in a fetch routine that can gracefully handle the absence of the requested object or (b) create an object (Command type?) to check for it.

Happy Thanksgiving,

William replied on Wednesday, November 22, 2006

Bayu replied on Thursday, November 23, 2006

Hey,

Isn't the fact that you didn't catch an exception the 'success' flag that you need?

Or don't you trust your sql or sproc?

Then you could implement a shared/static Exists function like this:

    Public Shared Function Exists(ByVal id As Guid) As Boolean
        Dim result As ExistsCommand = DataPortal.Execute(Of ExistsCommand)(New ExistsCommand(id))
        Return result.Exists
    End Function

    <Serializable()> _
    Private Class ExistsCommand
        Inherits CommandBase

        Private _ID As Guid
        Private _Exists As Boolean

        Public Sub New(ByVal id As Guid)
            Me._ID = id
        End Sub

        Public ReadOnly Property Exists() As Boolean
            Get
                Return Me._Exists
            End Get
        End Property

        Protected Overrides Sub DataPortal_Execute()
            Using cn As New MySqlConnection(Database.CrmDBConnection(True))
                cn.Open()
                Using cm As MySqlCommand = cn.CreateCommand

                    cm.CommandType = CommandType.Text
                    cm.CommandText = "SELECT COUNT(CustomerID) FROM Customer WHERE CustomerID = @id"
                    cm.Parameters.Add("?id", Me._ID)

                    Dim count As Integer = CInt(cm.ExecuteScalar)
                    Me._Exists = (count > 0)

                End Using
            End Using
        End Sub

    End Class


Note that in this case deletion takes 2 DB hits, but I guess your needs then would validate this.

Regards,
Bayu

gmclean replied on Monday, November 27, 2006

Thanks for all the suggestions. I had thought about another trip to the database to check that the record was deleted but I was hoping to avoid what I thought was an unnecessary database hit. I guess if data_portal.delete throws an exception that is really all that is needed since I can handle the exception in the calling program.

Thanks again for the suggestions,

George