Rx Android Xamarin - Signup form

RxSignUp.cs

// SignUp flow.
Observable.CombineLatest(
  firstName .RxTextChanged(50).StartWith(string.Empty),
  lastName  .RxTextChanged(50).StartWith(string.Empty),
  email     .RxTextChanged(50).StartWith(string.Empty),
  pwd       .RxTextChanged(50).StartWith(string.Empty),
  confirmPwd.RxTextChanged(50).StartWith(string.Empty),
  gender    .RxSelectedItem() .StartWith(0),
, Tuple.Create)
.SampleLatest(
  Observable.Merge(
    Observable.Merge(
      firstName .RxKeyPressed(),
      lastName  .RxKeyPressed(),
      email     .RxKeyPressed(),
      pwd       .RxKeyPressed(),
      confirmPwd.RxKeyPressed()
    ).Where(_ => _ == Keycode.Enter)
     .Select(_ => Unit.Default)
  , registerBtn.RxClick()
).Do(_ => {
  email.Error      = null;
  pwd.Error        = null;
  email.Error      = null;
  pwd.Error        = null;
  confirmPwd.Error = null;
}))
.Do(_ => HideKeyboard())
.Debounce(TimeSpan.FromSeconds(2))
.SelectMany(_ => 
  Service
    .SignUp(_)
    .WithProgressDialog())
.Subscribe(_ => 
  _.Match(OnSuccess, OnFailed));

void OnSuccess(User  u) {} // Do something
void OnFailed (Error e) {} // Do something
void HideKeyboard()     {} // Code to hide android keyboard.