Command Update

This page introduces how you can use Avalonia UI binding to initiate changes on a view model from controls like buttons that have a Command attribute.

For example, you can use this view model with an action defined in the method ButtonAction:

public class MainWindowViewModel : ViewModelBase
{
    private string _greeting = "Welcome to Avalonia!";

    public string Greeting
    {
        get => _greeting;
        set => this.RaiseAndSetIfChanged(ref _greeting,  value);
    }

    public void ButtonAction()
    {
        Greeting = "Another greeting from Avalonia";
    }
}

Then in the corresponding XAML define two controls:

<TextBlock Text="{Binding Greeting}" />
<Button Command="{Binding ButtonAction}" >Change It</Button>

This means that when the user clicks the button, Avalonia UI updates the view model by calling the ButtonAction method. This changes the Greeting property using the setter, so in turn the new greeting text is notified back to the text control on the UI.