How to call a Javascript function in aspx page - Modal with div

 ScriptManager.RegisterStartupScript(inboxContentUpdatePanel, inboxContentUpdatePanel.GetType(), Guid.NewGuid().ToString(), String.Format("OpenManageDirectoryModal();"), true);

function OpenManageDirectoryModal() {

            debugger;

            //var divManageDirectory = document.getElementById('divManageDirectory');

            //divManageDirectory.style.display = 'block';

            $("#modal_ManageDirectory").modal("show");

        }

<div class="modal fade" id="modal_ManageDirectory" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true" data-keyboard="false" data-backdrop="static" style="display: none;z-index:9999">

        <div class="modal-dialog bigmodal-dialog" role="document">

            <div class="modal-content">

                <asp:UpdatePanel ID="uc_modalupdatepanel" runat="server" UpdateMode="Always">

                    <ContentTemplate>

                        <uc1:UCManageDirectory runat="server" ClientIDMode="AutoID" ID="ucManageDirectory" />

                    </ContentTemplate>

                </asp:UpdatePanel>

            </div>

        </div>

    </div>