title: How can I search Active Directory by username using C#?
body: <p>I'm trying to search active directory by the username 'admin'. I know for a fact that there is a user with that username in the directory, but the search keeps coming back with nothing.</p>
  
  <pre><code>var attributeName = "userPrincipalName";
  var searchString = "admin"
  var ent = new DirectoryEntry("LDAP://"dc=corp,dc=contoso,dc=com")
  var mySearcher = new DirectorySearcher(ent);
  mySearcher.Filter = string.Format("(&amp;(objectClass=user)({0}={1}))", attributeName, searchString);
  
  var userResult = mySearcher.FindOne();
  </code></pre>
  
  <p>userResult always ends up null. I would love to know why, there must be something that I'm missing.</p>