<asp:ToolkitScriptManager ID="ToolkitScriptManager2" runat="server" EnablePageMethods="true"/>

....

<InsertItemTemplate>
                                        <asp:TextBox ID="tbFrom" runat="server" />
                                       <asp:AutoCompleteExtender ID="ace1" runat="server" TargetControlID="tbFrom" ServiceMethod="GetPlaces" MinimumPrefixLength="2" />

 [System.Web.Services.WebMethod, System.Web.Script.Services.ScriptMethod()]
        public string[] GetPlaces(string prefixText, int count)
        {
            return KB.GetPlaces(prefixText);
        }