private static IObservable <ProxyModel> AddProxy(
            this ProxyPopupContext context,
            IProxyManager proxyManager)
        {
            var proxy = new TdApi.Proxy
            {
                Server = null,
                Port   = 0,
                Type   = new TdApi.ProxyType.ProxyTypeSocks5
                {
                    Username = null,
                    Password = null
                }
            };

            var proxyModel = ProxyModel.FromProxy(proxy);

            return(Observable.Return(proxyModel));
        }
        private static IDisposable BindList(
            this ProxyPopupContext context,
            IProxyManager proxyManager)
        {
            return(proxyManager.GetAllProxies()
                   .SubscribeOn(RxApp.TaskpoolScheduler)
                   .ObserveOn(RxApp.MainThreadScheduler)
                   .Accept(proxies =>
            {
                var disabledProxy = ProxyModel.DisabledProxy();
                disabledProxy.EnableCommand = context.EnableProxyCommand;

                var otherProxies = Enumerable.Select <TdApi.Proxy, ProxyModel>(proxies, p =>
                {
                    var proxyModel = ProxyModel.FromProxy(p);
                    proxyModel.RemoveCommand = context.RemoveProxyCommand;
                    proxyModel.EnableCommand = context.EnableProxyCommand;
                    return proxyModel;
                })
                                   .ToList();

                context.Proxies = new ObservableCollectionExtended <ProxyModel>();
                context.Proxies.Add(disabledProxy);
                context.Proxies.AddRange(otherProxies);

                if (context.SelectedProxy == null)
                {
                    context.SelectedProxy = otherProxies.FirstOrDefault(p => p.IsEnabled)
                                            ?? disabledProxy;
                }

                if (!Enumerable.Any <TdApi.Proxy>(proxies, p => p.IsEnabled))
                {
                    disabledProxy.IsEnabled = true;
                }
            }));
        }