title: Most efficent way of joining strings
body: <p>I need to concatenate a lot of strings alltogether and put a comma between any of them.
  I have a list of strings</p>
  
  <pre><code>"123123123213"
  "1232113213213"
  "123213123"
  </code></pre>
  
  <p>and I want to get </p>
  
  <pre><code>"123123123213,1232113213213,123213123"
  </code></pre>
  
  <p>I was wondering what is the best way to achieve that.</p>
  
  <p>I could do this like this:</p>
  
  <pre><code>private List&lt;string&gt; stringList = new List&lt;string&gt; { 
      // a lot of strings in here
      "1234567890", "34343434", "4343434" }; 
  
  string outcome = string.Join(",", stringList.ToArray());
  </code></pre>
  
  <p>Or maybe:</p>
  
  <pre><code>StringBuilder builder = new StringBuilder();
  stringList.ForEach(val =&gt; {
      builder.Append(val);
      builder.Append(",");
  });
  
  string outcome = builder.ToString();
  </code></pre>
  
  <p>Which way is better? Do you know better ways to concatenate strings?</p>