问在vb.net中加载表单很慢

EN

 Private Sub pn()
     Try
        con = Class1.dbconn
        Dim dt As New DataTable
        Dim ds As New DataSet
        ds.Tables.Add(dt)
        Dim da As New SqlDataAdapter("select [Part Name] from 
                                      Part_Master_Download$", con)
        da.Fill(dt)
        Dim r As DataRow
        TextBox9.AutoCompleteCustomSource.Clear()
        For Each r In dt.Rows
            TextBox9.AutoCompleteCustomSource.Add(r.Item(0).ToString)

        Next
        con.Close()

    Catch ex As Exception
        MessageBox.Show(ex.Message)
    End Try
End Sub