title: Powershell Invoke() returns empty if I use AddParameter
body: <p>I have a C# script to mail-enable a distribution group in Exchange. I have tried the following code, which works currently:</p>
  
  <pre><code>Command command = new Command("Enable-DistributionGroup -Identity '#Test DL'");
  psInstance.Commands.AddCommand(command);
  </code></pre>
  
  <p>The above code works, and will return a string with the name of the distribution group. Upon checking the distribution group, it has become mail-enabled.</p>
  
  <p>The below code does not work, and returns an empty string:</p>
  
  <pre><code>Command command = new Command("Enable-DistributionGroup").AddParameter("Identity", "#Test DL");
  psInstance.Commands.AddCommand(command);
  </code></pre>
  
  <p>Am I using the AddParameter function incorrectly?</p>