async void Button_Clicked(System.Object sender, System.EventArgs e)
        {
            if (KindUser.SelectedIndex == -1)
            {
                DependencyService.Get <IMessage>().ShortAlert("Select a Kind of User !");
                return;
            }
            if (user_name.Text == "" || user_name.Text == null)
            {
                DependencyService.Get <IMessage>().ShortAlert("Enter User Name !");
                user_name.Focus();
                return;
            }
            if (Pass_Word.Text == "" || Pass_Word.Text == null)
            {
                DependencyService.Get <IMessage>().ShortAlert("Enter Password !");
                Pass_Word.Focus();
                return;
            }
            if (NickName.Text == "" || NickName.Text == null)
            {
                DependencyService.Get <IMessage>().ShortAlert("Enter NickName !");
                NickName.Focus();
                return;
            }
            string cc = "";

            if (AdminPage.idd == 0)
            {
                cc = "user_name=" + user_name.Text + "&pass="******"&nick=" + NickName.Text + "&knd=" + KindUser.SelectedIndex + "&id=" + 0;
            }
            else
            {
                cc = "user_name=" + user_name.Text + "&pass="******"&nick=" + NickName.Text + "&knd=" + KindUser.SelectedIndex + "&id=" + AdminPage.idd;
            }
            var action = await DisplayAlert("Online Examination", "Add " + " New User " + " ? ", "Yes", "No");

            if (action)
            {
                sav.IsEnabled = false;

                try
                {
                    var current = Connectivity.NetworkAccess;
                    if (current == NetworkAccess.Internet)
                    {
                        var formContent = new FormUrlEncodedContent(new[]
                        {
                            new KeyValuePair <string, string>("id", "1"),
                        });
                        string tt        = "https://onlineexamination.a2hosted.com/OnlineExamination/insert_user.php?" + cc;
                        var    response2 = await App.con.PostAsync(tt, formContent);

                        response2.Dispose();
                        CloseAllPopup();
                        MessagingCenter.Send <UserInfo>(this, "ref");
                    }
                }
                catch
                {
                }
                sav.IsEnabled = true;
            }
        }