title: Why is my format giving me an error when I try to format an enum to a string?
body: <p>I have the following enum:</p>
  
  <pre><code>public enum EReferenceKey {
          Accounts             = 1,
          Emails                = 3,
          Phones               = 4
  }
  </code></pre>
  
  <p>When my enum variable pk is Accounts and I try to convert this to "01" using</p>
  
  <pre><code>var a = pk.ToString("00");
  </code></pre>
  
  <p>it gives me the following exception:</p>
  
  <p>Format String can be only "G", "g", "X", "x", "F", "f", "D" or "d"</p>
  
  <p>Can someone explain what I am doing wrong?</p>