Using dropDownList control in DataGrid

<asp:dropdownlist id="dropdownlist1" runat="server"datasource="<%#  getcategory() %>"datatextfield="categoryname"datavaluefield="categoryid"selectedindex='<%# getcategoryid((string)databinder.eval(container.dataitem, "categoryname")) %>' />

using system;using system.collections;using system.componentmodel;using system.data;using system.data.oledb;using system.configuration;using system.drawing;using system.web;using system.web.sessionstate;using system.web.ui;using system.web.ui.webcontrols;using system.web.ui.htmlcontrols;namespace management{        public class dropdown : system.web.ui.page    {        protected system.web.ui.webcontrols.datagrid productgrid;        protected datatable _category;        //new a database class to get records, productdb is a public class         //containing several functions        protected productdb pdb=new productdb();            public dropdown()        {            page.init += new system.eventhandler(page_init);        }        private void page_load(object sender, system.eventargs e)        {            if(!ispostback)            {                bindproduct();                            }        }        private void page_init(object sender, eventargs e)        {            initializecomponent();        }        void bindproduct()        {            //pdb.getproduct() returns a datatable to product's datagrid            productgrid.datasource=pdb.getproduct();            productgrid.databind();        }        protected void product_edit(object sender, datagridcommandeventargs e)        {                        bindcategory();            ((datagrid)sender).edititemindex=e.item.itemindex;            bindproduct();        }        protected void product_cancel(object sender, datagridcommandeventargs e)        {            productgrid.edititemindex=-1;            bindproduct();        }        protected void product_update(object sender, datagridcommandeventargs e)        {            //get the currnet product name            string pname=e.item.cell[1].controls[0].text;            //get the current product price            string price=e.item.cell[2].controls[0].text;            //get the current categoryid    dropdownlist ddl=(dropdownlist)e.item.cells[3].findcontrol("dropdownlist1");            string categoryid=ddl.selecteditem.value;            //get the current productid            string pid=e.item.cell[4].controls[0].text;            //call pdb's update function            pdb.update(pid,pname,price,categoryid);                        productgrid.edititemindex=-1;            bindproduct();                    }        void bindcategory()        {            //pdb.fetchcategory() returns a datatable            _category=pdb.fetchcategory();                            }        protected datatable getcategory()        {            return _category;        }        protected int getcategoryid(string cname)        {            for(int i=0;i<_category.defaultview.count;i++)            {            if (_category.defaultview[i]["categoryname"].tostring()==cname)                {                    return i;                }            }            return 0;                        }        #region web form designer generated code        ///         /// required method for designer support - do not modify        /// the contents of this method with the code editor.        ///         private void initializecomponent()        {                this.load += new system.eventhandler(this.page_load);        }        #endregion            }}