Caution: when you are using strongly typed models in MVC3 and you modify a property of the model in an Action, that property will get discarded when you create the view unless you clear the ModelState first. When building the view, the model fields are overwritten with values from ModelState, so clearing the ModelState prevents this.
UPDATE 11/10/2011:
This only applies to values passed in via a POST (or a GET?) that you're attempting to override by changing the corresponding fields in the view model.
UPDATE 11/10/2011:
This only applies to values passed in via a POST (or a GET?) that you're attempting to override by changing the corresponding fields in the view model.