title: ASP.NET MVC ModelState how to re-run validation
body: <p>I am trying to "re-run" validation of ModelState after I change model within my controller. Is this possible to do? Here is code example that explains it:</p>
  
  <pre><code>[HttpPost]
  [ValidateAntiForgeryToken]
  public ActionResult ContactUs(ContactUsModel model)
  {
      model.Email = "defaultemail@world.com";
  
      // Email is required field and even though it's 
      // now valid ModelState.IsValid is false
      // how to re-run validation?
      if (ModelState.IsValid)
      {
          // want to get here
      }
  }
  </code></pre>