c# - SqlDataSource parameter from codebehind -

i using sql datasource , checkboxlist filter datalistview. want make parameter sqldatasource code behind , use sql in filter datalistview rows. when check 1 checkbox in checkboxlist work great... when check more 1 checkbox datalist view takes no data. onselecting code sql datasource:

protected void ds_subgroupid_changed_selecting(object sender,sqldatasourceselectingeventargs e) {     list<string> selected = new list<string>();     foreach (listitem item in checkboxlist_subgroup.items)         if (item.selected)         {             selected.add(item.value);         }      string commaselect = string.join(",", selected.toarray());     e.command.parameters["@product_subgroup"].value = commaselect;   } 

and here sqldatasource control:

<asp:sqldatasource id="ds_subgroupid_changed" runat="server"    connectionstring="<%$ connectionstrings:nimrokhdbconnectionstring %>"     selectcommand="select * [tbl_product] (([product_group] = @product_group) , ([product_subgroup] in (@product_subgroup)))"    onselecting="ds_subgroupid_changed_selecting">         <selectparameters>             <asp:controlparameter controlid="radio_list_group" name="product_group" propertyname="selectedvalue" type="string" />             <asp:parameter name="product_subgroup" />         </selectparameters>         </asp:sqldatasource> 

i have 1 table subgroup contains subgroupid int , subgroupname, , have table product contan subgroup store subgroup id in nvarchar. wonder if cause problem. because checkboxlist value set subgroupid form subgroup table.

i appretiate help. thank guys.