Question

I have a textbox and a dropdownlist on my client side. I need to pass the values of these controls to a webmethod (in the code behind) using javascript.
I can pass the textbox value but not the dropdownlist.

<p><asp:DropDownList id="ddlList" runat="server"></asp:DropDownList></p>
<p><asp:TextBox ID="txtSearch" runat="server"  OnTextChanged="txtSearch_TextChanged"    OnKeyPress="onKeyFunction();" AutoPostBack="True"></asp:TextBox>
<asp:GridView ID="grdLista" runat="server"></asp:GridView>

<script type="text/javascript">
    function onKeyFunction() {
        var search = document.getElementById('<%=txtSearch.ClientID %>').value;
        //var ddl = i need to pass the dropdownlist values here..
        PageMethods.callJS(search, /*ddl */, onSucess, onError);

        function onSucess(result) {
            alert(result);
        }

        function onError(result) {
            alert('Something wrong.');
        }
    }
</script>

And this is the code in my WebMethod

[WebMethod]            
public static IEnumerable<string> callJS(string search)
{
    IEnumerable<string> results = itemList.Where(item => item.Contains(search.ToLower()));
    return (results);
}

Answer 1

You can get the value of your DDL like this :

var liste =  document.getElementById('#ddlList');
var ddl = liste.options[liste.selectedIndex].value;

---

EDIT :

In order to retrieve all the values from a DDL, we have to loop over the options values:

var ddl = [];
for(var i = 0; i<3; i++) {
    ddl.push(document.getElementById("<%=ddlList.ClientID %>").options[i].value);
}

This array can be get at server side as a List<string>:

[WebMethod()]
public static IEnumerable<string> callJS(List<string> ddl) { ... }