public PackageChooserViewModel(IMruPackageSourceManager packageSourceManager)
        {
            Packages = new ObservableCollection<PackageInfo>();
            NavigationCommand = new NavigateCommand(this);
            SortCommand = new RelayCommand<string>(Sort, column => TotalPackageCount > 0);
            SearchCommand = new RelayCommand<string>(Search);
            LoadedCommand = new RelayCommand(() => Sort("VersionDownloadCount", ListSortDirection.Descending));
            ChangePackageSourceCommand = new RelayCommand<string>(ChangePackageSource);
            _credentialProvider = new AutoDiscoverCredentialProvider();
            _proxyService = new ProxyService(_credentialProvider);

            _packageSourceManager = packageSourceManager;
        }