title: How Can I forbid repeated characters using regular Expression
body: <p>How Can I forbid repeated characters using regular Expression? </p>
  
  <p>This regular Expression should not allow </p>
  
  <pre><code>1--234567890
  1--2345--1212
  </code></pre>
  
  <p>However following is valid</p>
  
  <pre><code>1-2-3-4-5-6-7-8-9-0
  1234567890
  </code></pre>
  
  <p>The only concern here is minus cannot be entered  after each other, so <code>--</code> should not match</p>
  
  <p>There is no restriction in how many dash are in string.
  I'm using C#</p>
  
  <p>Thanks in Advance</p>