title: string Join List and items
body: <p>I need to join strings and <code>List&lt;string&gt;</code> items. My Code</p>
  
  <pre><code>List&lt;string&gt; list = new List&lt;string&gt;() { "item1", "item2" };
  string item3 = "item3";
  
  string result = string.Join(",", list, item3); 
  </code></pre>
  
  <p>The result is</p>
  
  <pre><code>//System.Collections.Generic.List`1[System.String],item3
  </code></pre>
  
  <p>instead of expected</p>
  
  <pre><code>//item1,item2,item3
  </code></pre>
  
  <p>What is the most elegant approach so solve this inline? There could be multiple <code>List&lt;string&gt;</code> and multiple <code>string</code> and each of them can be null.</p>