title: PropertyDescriptor and WPF Binding mechinsm
body: <h2>Background</h2>
  
  <p>I am investigating some code and encountered a xaml containing a <code>DataGrid</code> with some binded columns:</p>
  
  <pre><code>Binding="{Binding calc_from}" ....
  </code></pre>
  
  <p>I've search everywhere but there is no class containing a property called <code>calc_from</code>.
  Then I stumbled upon some <code>PropertyDescriptor</code> classes. I figured that this is how they make the binding work but didn't fully understand how.</p>
  
  <h2>Question</h2>
  
  <p>What is <code>PropertyDescriptor</code> and what is it good for?
  When will I want to implement my own <code>CustomTypeDescriptor</code>?
  And how does it relate to WPF binding mechanism?</p>
  
  <p>I've came accross an example in <a href="https://stackoverflow.com/questions/1834454/wpf-data-binding-example-of-custom-type-descriptor">this</a> thread but I'd be happy if someone will shed some light on it</p>