scene: when I click item in ext:ComboBox and want to set the item selected value to cookie variable. Finally, after I click ext:Button, the ext:Label get cookie value and display it. But I get a error :Ext.Ajax Communication Failure , any help will be appreciated. aspx: <ext:ComboBox ID="ComboBox1" runat="server" StoreID="Store1" Width="100" Editable="false" DisplayField="name" ValueField="value" Mode="Local" TriggerAction="All`enter code here`" EmptyText="Select a locale..."> ..... aspx.cs protected void lngIndexChanged(object sender, DirectEventArgs e) { //Sets the cookie that is to be used by Global.asax HttpCookie cookie = new HttpCookie("CultureInfo"); cookie.Value = ComboBox1.SelectedItem.Value ; Response.Cookies.Add(cookie); Label1.Text = cookie.Value; //Set the culture and reload for immediate effect. //Future effects are handled by Global.asax Thread.CurrentThread.CurrentCulture = new CultureInfo(ComboBox1.SelectedItem.Value); Thread.CurrentThread.CurrentUICulture = new CultureInfo(ComboBox1.SelectedItem.Value); }