title: Using StringBuilder.Append() in a lambda expression is producing an empty string
body: <p>I'm trying to append a list of strings(> 10),so to avoid creating a lot of strings I am using a StringBuilder.It would be great if someone explains why this is happening..</p>
  
  <pre><code>using System;
  using System.Text;
  using System.Collections.Generic;
  using System.Linq;
  
  public class Program
  {
      public static void Main()
      {
          var lst = new List&lt;string&gt;(){"A", "B", "C"};
          StringBuilder sb = new StringBuilder();
          lst.Select(str =&gt; sb.Append(str.ToLower()));
          Console.Write("Output: {0}", sb.ToString());
      }
  }
  </code></pre>
  
  <p><a href="https://dotnetfiddle.net/wJ8rKU" rel="nofollow noreferrer">Run the code here-dotnetfiddle</a></p>