title: Does string.Replace("a", "b") automatically check if "a" exists?
body: <pre><code>string banana = "banana apple";
  banana.Replace("apple", "pie");
  </code></pre>
  
  <p>If I want to replace apple with pie, can I do it like that, or do I need to use the following?</p>
  
  <pre><code>if(banana.Contains("apple"))
      banana.Replace("apple", "pie");
  </code></pre>