title: Regular expression for alphanumeric and underscore c#
body: <p>I am working with ASP.NET MVC 5 application in which I want to add dataannotation validation for Name field.</p>
  
  <p>That should accept any combination of number,character and under score only.</p>
  
  <p>I tried by this but not working :</p>
  
  <pre><code>RegularExpression("([a-zA-Z0-9_ .&amp;'-]+)", ErrorMessage = "Invalid.")]
  </code></pre>