title: Validate on multiple errors with one CustomValidator
body: <p>I am trying to figure out how to use Validation on Business Objects. </p>
  
  <p>Until now I have only seen examples on <em>CustomValidator</em> that checks for only 1 error. I have two fields with DateTime input that should check for 3 or more errors. I guess normally I should check on client, then on server, last on database level. </p>
  
  <ul>
  <li>If I get an error on a field, I should not be able to leave the field. </li>
  <li>On the Client Validation this is not an error that should cause an Exception since it's only a user error. But if something goes wrong and the user bypass the Client Validation, the Server Validation should kick an Exception. </li>
  <li>And last, if i have other e.g. Batch Update work then they should use the Database Validation code. Please correct me if I have missed something fundamental! </li>
  </ul>
  
  <ol>
  <li>`dateFrom` is not empty. (But `dateTo`can be empty)  </li>
  <li>`dateFrom` is earlier than `dateTo`</li>
  <li>`dateFrom` and `dateTo` is within constant `MinDate` and `MaxDate`</li>
  </ol>  
  
  <p>So How should my Validation look like, Client, Server and Database?</p>
  
  <p><em>Thoughts</em>: </p>
  
  <p>Should the validation logic be separated on 3 different places; UI, Code and DataObject(Database)? When it is the exact same code? Seems redundant?</p>
  
  <p>Can I use the same validation method for all three checks? Or do I need to implement 3  code-chunks, and 3 Methods for each, and then how do I list all in the ValidationSummary nicely?</p>