. NET background fetch JS assigned value to Hidden

 <script type= "Text/javascript" >//with "Select All" check box as parameter function Checkall () {var checkall = Document.getelement        Byid ("All");        var Checkitem = document.getelementsbytagname ("input"); for (var i = 0; i < checkitem.length; i++) {if (checkitem[i].type== "checkbox") {Checkitem[i].            checked = checkall.checked;            }}}//Gets the selected check box function Update () {var chkitems = document.getelementsbyname ("Item");                       var bookId = "";                    for (var i = 0; i < chkitems.length; i++) {if (chkitems[i].checked) {                BookId + = Chkitems[i].value + ",";                      }} bookId = Bookid.substr (0, bookid.length-1);                document.getElementById (' <%=hidBookId.ClientID%> '). Value = BookId;        Alert (document.getElementById (' <%=hidBookId.ClientID%> '). Value); }</script>

HTML code:

<input type= "checkbox" id= "All" onclick= "Checkall ()"/> Select all <input type= "checkbox" Name= "Item" value= "<%# Eval ("Id")%> "/>

  <input type= "hidden" id= "Hidbookid"  name= "Hidbookid" runat= "Server"/> The      selected books are categorized in: <asp:d Ropdownlist id= "ddlcategory" runat= "Server" ></asp:DropDownList>  <asp:button id= "Btncategory" runat = "Server" text= "Modify  " onclick= "Btncategory_click"  onclientclick= "Update ();"/>

　

Background code:

Using system;using system.collections.generic;using system.linq;using system.web;using System.Web.UI;using System.web.ui.webcontrols;using model;using bll;public partial class listbooksbycategory:system.web.ui.page{Prote CTED void Page_Load (object sender, EventArgs e) {if (!            IsPostBack) {categorybind ();                Booksbind (); }}///<summary>//Binding Data///</summary>//<param name= "PM" ></param> PR otected void Booksbind () {list<book> List = new Bookmanager ().        Getallbooks ();        This.gvBooks.DataSource = list;    This.gvBooks.DataBind (); }///<summary>//binding book type name///</summary> protected void Categorybind () {this.ddlcate Gory. DataSource = new Categorymanager ().        Getallcategory ();        This.ddlCategory.DataTextField = "Name";        This.ddlCategory.DataValueField = "Id";    This.ddlCategory.DataBind (); } protectedvoid Gvbooks_pageindexchanging (object sender, Gridviewpageeventargs e) {//Get index number This.gvBooks.PageIndex        = E.newpageindex;    Booksbind (); }///<summary>///Click Modify button Events///</summary>//<param name= "sender" ></param>/// Lt;param name= "E" ></param> protected void Btncategory_click (object sender, EventArgs e) {str       ing strbookid = this.hidBookId.Value;       string[] Array = strbookid.split (', '); for (int i = 0; i < array. Count ();           i++) {int categoryId = Convert.ToInt32 (This.ddlCategory.SelectedValue); New Bookmanager ().       Updatecategoryidbyid (Convert.ToInt32 (Array[i]), categoryId);    } booksbind (); }}

　　

. NET background fetch JS assigned value to Hidden