مشكلة في إضافة الصنف بالباركود في الفاتورة

كود :
Private Sub TB_item_barcode_Leave(sender As Object, e As EventArgs) Handles TB_item_barcode.Leave

        '\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ طريقة الإدخال بالباركود \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

        '\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\



        Dim BAR_ As Integer



        If TB_item_barcode.Text <> Nothing Then

            Dim DT As New DataTable

            Dim DA As New SqlClient.SqlDataAdapter("SELECT * FROM Item WHERE item_barcode like '" & TB_item_barcode.Text & "'", connSQLServer)

            DA.Fill(DT)



            If DT.Rows.Count > 0 Then



                '\\\\\\\\\\\\\\\\\\\\\التحقق من رقم كود الصنف\\\\\\\\\\\\\\\\\\\\\

                For I As Integer = 0 To DataGridView.Rows.Count - 1

                    If DataGridView.Rows(I).Cells(0).Value = DT.Rows(0).Item("item_id") Then

                        DataGridView.Rows(I).Cells(4).Value = DataGridView.Rows(I).Cells(4).Value + 1

                        TB_item_barcode.Clear()

                        Exit Sub

                    End If

                Next



                '\\\\\\\\\\\\\\\\\\\\\إضافة سجل للداتاجيرد\\\\\\\\\\\\\\\\\\\\\



                DataGridView.Rows.Add()

                BAR_ = DataGridView.Rows.Count - 1

                DataGridView(0, DataGridView.Rows.Count - 1).Value = DT.Rows(0).Item("item_id")

                DataGridView(1, DataGridView.Rows.Count - 1).Value = DT.Rows(0).Item("item_name")

                DataGridView(2, DataGridView.Rows.Count - 1).Value = DT.Rows(0).Item("item_barcode")

                DataGridView(3, DataGridView.Rows.Count - 1).Value = DT.Rows(0).Item("item_price")

                DataGridView(4, DataGridView.Rows.Count - 1).Value = 1

            End If

        End If

    End Sub





    Private Sub TB_item_barcode_KeyDown(sender As Object, e As KeyEventArgs) Handles TB_item_barcode.KeyDown

        If e.KeyCode = Keys.Enter Then

            TB_item_barcode_Leave(sender, e)

        End If

    End Sub