title: ASP.Net MVC 3 ModelState.IsValid
body: <p>I am just getting started with ASP.Net MVC 3 and am confused on this point.</p>
  
  <p>In some examples when an action in a controller is run that contains inputs then a check is made to ensure ModelState.IsValid is true. Some examples do not show this check being made. When should I make this check? Must it be used whenever an input is provided to the action method? </p>