title: Why Convert.ToInt32(null) returns 0 in c#
body: <p>I just came across this today, if you convert null to int32 </p>
  
  <pre><code>Convert.ToInt32(null)
  </code></pre>
  
  <p>it returns 0</p>
  
  <p>I was expecting an InvalidCastException...</p>
  
  <p>Any idea why this happen?</p>