ShowModalAletView.cs

int ShowModalAletView (string title, string message, params string[] buttons)
{
    int clicked = -1;
    var alertView = new UIAlertView (title, message,  null, null, buttons);
    alertView.Show ();
    bool done = false;
    alertView.Clicked += (sender, buttonArgs) => {
        Console.WriteLine ("User clicked on {0}", buttonArgs.ButtonIndex);
        clicked = buttonArgs.ButtonIndex;
    };    
    while (clicked == -1){
        NSRunLoop.Current.RunUntil (NSDate.FromTimeIntervalSinceNow (0.5));
    }
    return clicked;
}