title: Equivalent of (VB6) IsMissing in C#?
body: <p>Here's what I get in VB6 Description:</p>
  
  <p><a href="https://i.stack.imgur.com/NukWe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NukWe.png" alt="enter image description here"></a></p>
  
  <p>How to do this in c#?</p>
  
  <p><strong>P.S.</strong> I also don't know how to use optional parameter in c#.</p>