title: Is there a more elegant way to merge observables when return type is unimportant?
body: <p>I have a ReactiveUI-like view model. It has several properties of different types which fire <code>NotifyPropertyChanged</code> events and I want to subscribe a method that will be called when any is fired, but I am not interested in actual values.</p>
  
  <p>My current code is a bit ugly (due to opaque <code>true</code> selects). Is there a way to express this which shows the intention of just caring when the event occurs?</p>
  
  <pre><code>    this.ObservableForProperty(m =&gt; m.PropertyOne)
          .Select(_ =&gt; true)
          .Merge(this.ObservableForProperty(m =&gt; m.PropertyTwo).Select(_ =&gt; true))
     .Subscribe(...)
  </code></pre>
  
  <p>I am merging about 8 properties, so it's more ugly than shown.</p>