YES It is POSSIBLE , use ajax control toolkit's combobox , like this :
<asp:ComboBox ID="comPosition" runat="server" AppendDataBoundItems="True" AutoCompleteMode="Suggest" AutoPostBack="True" DataSourceID="rdCombo" DataTextField="cont_name" DataValueField="cont_id" MaxLength="0" style="display: inline;">
</asp:ComboBox>
<asp:SqlDataSource ID="rdCombo" runat="server" ConnectionString="<%$ ConnectionStrings:ABCConnectionString %>"
SelectCommand="SELECT * FROM [sd_m_country]"></asp:SqlDataSource>
don't forget to put this above the above coding :
<asp:ToolkitScriptManager ID="ProfileScriptManger" EnablePageMethods="True" runat="server"></asp:ToolkitScriptManager>
Download AjaxControlToolKit from here
http://www.asp.net/ajaxlibrary/act.ashx