title: Role of Parameterless constructor in WPF (XAML)
body: <p>I've been reading an online tutorial on <a href="http://wpftutorial.net/XAML.html" rel="noreferrer">WPF</a>, there I read a line 
  "All classes in WPF have parameterless constructors and make excessive usage of properties. That is done to make it perfectly fit for XML languages like XAML."</p>
  
  <p>I examined above words by creating a custom class with one parameterized constructor and encountered error "Type 'custom_class_name' is not usable as an object element because it is not public or does not define a public parameterless constructor or a type converter."</p>
  
  <p>I just wanted to know a specific detailed reason, how parameterless constructors help achieving this.</p>