<asp:Button ID="BtnSubmit" runat="server" Text="修改" OnClick="BtnSubmit_Click" OnClientClick="return formSubmit('true');" />

<script type="text/javascript">

                function formSubmit(val) {

                    if (val== "true")

                    {

                        form1.submit();

                    } else {

                        return false;

                    }

                }

            </script>