title: is assign null to a variable enforce release memory or dispose varaible
body: <p>Can anyone please tell me </p>
  
  <ol>
  <li>What is the benefit of assigning <code>null</code> to variable after use ?</li>
  <li>What is the meaning of assigning <code>null</code> after disposing a object ?</li>
  <li>How does GC work?</li>
  </ol>
  
  <p>Thanks in advance</p>