Created Unassigned: Get SelectedValue not SelectedText from Combobox in Javascript [27513]

My DataSource is a EntityFramework .toList()
I need to get from Javascript the SelectedValue not SelectedText or SelectedIndex...

here is My ComboBox declaration

<asp:ComboBox ID="FK_Countries" runat="server"
DataTextField="PLAYER_NAME_EN"
DataValueField="ID"
AutoPostBack="True" OnSelectedIndexChanged="FK_Countries_SelectedIndexChanged" AutoCompleteMode="Suggest" DropDownStyle="DropDownList" RenderMode="Block" EnableTheming="True" />


this is the row in page load under the !IsPostback ...

this.FK_Countries.DataSource = db.Countries.OrderBy(o => o.PLAYER_NAME_EN).ToList();


i see more examples on google but anyone work for me...
thanks in advance
Flavio