title: Check null in C# 6 with default value
body: <p>I am using <strong>C# 6</strong> and I have the following:</p>
  
  <pre><code>public class Information {
    public String[] Keywords { get; set; }
  }
  
  Information information = new Information {
    Keywords = new String[] { "A", "B" };
  }
  
  String keywords = String.Join(",", information?.Keywords ?? String.Empty);
  </code></pre>
  
  <p>I am checking if information is null (in my real code it can be). If it is than join a String.Empty since String.Join gives an error when trying to join null. If it is not null then just join information.Keywords.</p>
  
  <p>However, I get this error:  </p>
  
  <pre><code>Operator '??' cannot be applied to operands of type 'string[]' and 'string'
  </code></pre>
  
  <p>I was looking on a few blogs and supposedly this would work. </p>
  
  <p>Am I missing something?</p>
  
  <p>What is the best alternative to do this check and join the string in one line?</p>