Moving event handling to ViewModel

Suppose that when a Button is pressed, we want to handle that fact in the ViewModel, as is preferred by the Model-View-ViewModel (MVVM) pattern. However, one of the things we want to do, in response to that Button press, is to show a ProgressBar.

Handling things in ViewModel gets tricky when we want to interact with the user interface (UI). However, it can be done in a number of ways. Let’s modify the Submit button, remove its Clicked event and add a command:

<Button
    BackgroundColor="Gray"
    Command="{Binding SubmitCommand}"
    Margin="5"
    Text="Submit" />

We’ll create RelayCommand in ViewModel to handle the Submit Command:

[RelayCommand]
private async void Submit()
{
  for (var i = 0.0; i < 1.0; i += 0.1)
  {
    await LoginPage.LoginProgressBar...