How to update UI in other threads Observable.Start

[107295472]

` public class MainViewModel : ReactiveObject
{
private int _txNum;
private int _aliOssNum;
private double _per;
public MainViewModel()
{
_txNum = 0;
_aliOssNum = 0;
_per = 0;
BtnStart = ReactiveCommand.CreateFromObservable(BtnStartImpl);
}
public ReactiveCommand<Unit, Unit> BtnStart { get; private set; }
public IObservable BtnStartImpl()
{
return Observable.Start(() =>
{
Per = 22;
});
}
public int TxNum
{
get => _txNum;
set => this.RaiseAndSetIfChanged(ref _txNum, value);
}

    public int AliOssNum
    {
        get => _aliOssNum;
        set => this.RaiseAndSetIfChanged(ref _aliOssNum, value);
    }
    public double Per
    {
        get => _per;
        set => this.RaiseAndSetIfChanged(ref _per, value);
    }
}`