title: Expression error in combining optional parameter
body: <p>When i click the print button am getting expression error
  Here, I am passing three parameter namely printername, printertray, no.of copies. Out of these three the printer tray is optional. Because the tray selection is not mandatory in all the cases.</p>
  
  <pre><code>public bool Print(string printerName, string printerTray=null,int? copies=1) {
  if(copies == null || copies &lt; 1) return false;        
  
  if (printerName.IsDefined() &amp;&amp; printerTray.IsDefined()) {
                      project.Regions[0].Device.Name = "\" " + "\
  
  "".Combine(printerName, printerTray)  +"\" ";
  }
  </code></pre>
  
  <p>I am getting an expression error when I try to combine the parameter.
  Can anyone help me am new to this .net</p>