ReactiveUI Example

RxUIExample.cs

public class MyViewModel : ReactiveObject
{
    private readonly ReactiveCommand<object> saveCommand;
    private readonly ObservableAsPropertyHelper<string> fullName;
    private readonly ObservableAsPropertyHelper<string> initials;
    private string firstName;
    private string lastName;
    private bool showLastNameFirst;

    public MyViewModel()
    {
        var canSave = this
            .WhenAnyValue(
                x => x.FirstName,
                x => x.LastName,
                (first, last) => !string.IsNullOrEmpty(first) && !string.IsNullOrEmpty(last));
        this.saveCommand = ReactiveCommand.Create(canSave);
        this.saveCommand.Subscribe(_ => { /* save data */ });

        this.fullName = this
            .WhenAnyValue(
                x => x.FirstName,
                x => x.LastName,
                x => x.ShowLastNameFirst,
                (first, last, showLastFirst) => showLastFirst ? string.Format("{0} {1}", last, first) : string.Format("{0} {1}", first, last))
            .ToProperty(this, x => x.FullName);
        this.initials = this
            .WhenAnyValue(
                x => x.FirstName,
                x => x.LastName,
                (first, last) => (string.IsNullOrEmpty(first) ? "" : first.Substring(0, 1) + (string.IsNullOrEmpty(last) ? "" : last.Substring(0, 1))))
            .ToProperty(this, x => x.Initials);
    }

    public ReactiveCommand<object> SaveCommand => this.saveCommand;

    public string FullName => this.fullName.Value;

    public string Initials => this.initials.Value;

    public string FirstName
    {
        get { return this.firstName; }
        set { this.RaiseAndSetIfChanged(ref this.firstName, value); }
    }

    public string LastName
    {
        get { return this.lastName; }
        set { this.RaiseAndSetIfChanged(ref this.lastName, value); }
    }

    public bool ShowLastNameFirst
    {
        get { return this.showLastNameFirst; }
        set { this.RaiseAndSetIfChanged(ref this.showLastNameFirst, value); }
    }
}