Question

I want to know what the advantage are using the relay command to call functions that refresh the screen. In my application I have the following relay command setup.

private RelayCommand _refreshSitesCommand;
    public RelayCommand RefreshSitesCommand
    {
        get { return _refreshSitesCommand ?? (_refreshSitesCommand = new RelayCommand(RefreshSites)); }
    }

    private RelayCommand _refreshProvidersCommand;
    public RelayCommand RefreshProvidersCommand
    {
        get { return _refreshProvidersCommand ?? (_refreshProvidersCommand = new RelayCommand(RefreshProviders)); }
    }

    private async void RefreshSites()
    {
        var sitesStats = await _dataService.GetSiteStats();

        if (sitesStats != null)
        {
            SiteStats.Clear();

            foreach (var site in sitesStats)
            {
                SiteStats.Add(new SiteStatsViewModel(site));
            }

            SelectedSite = SiteStats[0];
        }
    }

    private async void RefreshProviders()
    {
        var providers = await _dataService.GetProviders();

        if (providers != null)
        {
            Providers.Clear();

            foreach (var provider in providers)
            {
                Providers.Add(new ProviderViewModel(provider));
            }

            SelectedProvider = Providers[0];
        }
    }

Then in my code I have the following calls to execute it.

RefreshProvidersCommand.Execute(null);
RefreshSitesCommand.Execute(null);

So why is that better than just calling the RefreshSites and RefreshProviders functions. Then I would not need the code for the RelayCommand objects. Other than exposing the functionality of the 2 private functions, what benefit does using the RelayCommand object have over just making the functions public and calling them.

Answer 1

Because you can bind to a Command in your view. You can’t bind to methods in your views (well you can but binding to Commands is much cleaner)