Locate and edit row in Acces Database Table throws "Object Reference not set to an instance of object"

I save data in an Access Database table named TraiteTravail, with it primary key field namedid and want to edit a specific row, but I get this:

"""An unhandled exception of type 'System.NullReferenceException' occurred in SNIGDoFFE.exe

Additional information: Object reference not set to an instance of an object."""

but When I look in my database, the row with the id specified, exits in the table"TraiteTravail"

Dim SNIGDoFFEDataSet As SNIGDoFFE.SNIGDoFFEDataSet = CType(Me.FindResource("SNIGDoFFEDataSet"), SNIGDoFFE.SNIGDoFFEDataSet)

Dim SNIGDoFFEDataSetTraiteTravailTableAdapter As SNIGDoFFE.SNIGDoFFEDataSetTableAdapters.TraiteTravailTableAdapter = New SNIGDoFFE.SNIGDoFFEDataSetTableAdapters.TraiteTravailTableAdapter()

Dim TraiteTravailRow As SNIGDoFFEDataSet.TraiteTravailRow = SNIGDoFFEDataSet.TraiteTravail.FindByid(MainWindow.IdCas)

'edit some fields
TraiteTravailRow.T1_DateIdentification = t1.Text
TraiteTravailRow.T2_MoisSeparation = t2.Text
TraiteTravailRow.T2_AnneeSeparation = t2_.Text
'to update the table with the new added data, I suppose
SNIGDoFFEDataSetTraiteTravailTableAdapter.Update(TraiteTravailRow)

so I'm wondering what I've done wrong, why the FindByid, not work here,

Please, help me.