Dim myConnection As New OleDbConnection(connectionString)
        Dim myAdapter As New OleDbDataAdapter()
        myAdapter.SelectCommand = New OleDbCommand(commandString, myConnection)
        Dim myCommandBuilder As OleDbCommandBuilder = New OleDbCommandBuilder(myAdapter)
        Dim custDS As DataSet = New DataSet()

        myConnection.Open()

        myAdapter.Fill(custDS)

        ' Обновление происходит'
        custDS.Merge(myDataSet)

        ' а количество добавленных записей = 0'
        Dim count As Integer = myAdapter.Update(custDS)

        myConnection.Close()

    Public Shared Function GetDataSet(ByVal commandString As String) As DataSet
        Dim myConnection As OleDbConnection = New OleDbConnection(connectionString)
        Dim myCommand As New OleDbCommand(commandString, myConnection)
        Dim myAdapter As New OleDbDataAdapter(myCommand)
        Dim generatedDataSet As New DataSet()

        Try
            myAdapter.Fill(generatedDataSet)
        Catch err As Exception
            Dim q As String = err.Message
        Finally
            If (Not myConnection Is Nothing) Then
                myConnection.Close()
            End If
        End Try
        Return generatedDataSet
    End Function