title: Check constraint to validate IP address field
body: <p>I'm working on a project involving C# and a SQL Server 2008 database.
  In one of the tables, I have a field (<code>nvarchar(15)</code>) which will contain an IP address.</p>
  
  <p>I'd like to add a check constraint which will validate that the input value is actually an IP address.</p>
  
  <p>I wanted to use a regex to do that, but it seems that this feature is not supported by default.  I saw things about writing a customm dll with UDF inside (<a href="http://msdn.microsoft.com/en-us/magazine/cc163473.aspx" rel="nofollow noreferrer" title="MSDN Tutorial">MSDN tutorial</a>), but I don't really understand how it works (i.e. where should I place the dll ?)</p>
  
  <p>Is there a "simple" way to add such a constraint ?
  Any solution is welcome.</p>
  
  <p>Thanks in advance !</p>