mvvm command usage complete example

mvvmexample.txt

//the command:

        private RelayCommand logInCommand;

        public RelayCommand LogInCommand
        {
            get
            {
                return logInCommand ?? 
                    (logInCommand = new RelayCommand( 
                            async ()  =>
                                {
                                    IsBusy = true;
                                    ToggleKeypadCommand.Execute(null);
                                    using (var httpRequest = new HttpRequestService())
                                    {
                                        LoggedInUser = await httpRequest.GetUserAsync(Username);

                                        if (LoggedInUser != null)
                                        {                                      
                                            IsBusy = false;
                                            Username = string.Empty;
                                            _navigationService.NavigateTo("MainMenu", new UserViewModel { User = LoggedInUser });
                                        }
                                    }
                                },
                                         LogInCommandCanExecute));
            }
        }       

//the 	client	(droid)

_logInButton.SetCommand("Click", ViewModel.LogInCommand);

//the http request service

        public async Task<User> GetUserAsync(string userName)
        {
            using (var helper = new HttpClientFactory())
            {
                var result = await helper.GetAsync($"/accounts/user/{userName}");
                //todo add validation service
                if (!string.IsNullOrEmpty(result))
                {
                    var user = JsonConvert.DeserializeObject<User>(result);
                    return user;
                }

                return null;
            }
        }
		
//http client factory
        public async Task<string> GetAsync(string relativeUrl) 
        {
            var url = GetValidUrl(Constants.BaseUriDeployed, relativeUrl);
            using (var client = new HttpClient(new NativeMessageHandler()))
            {
                var response = await client.GetAsync(url);
                if (response.IsSuccessStatusCode)
                {
                    var result = await response.Content.ReadAsStringAsync();
                    return result;
                }
                return string.Empty;
            }
        }