Update the model on HttpPost and render the changes in the View
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by Etienne Giust
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Published on Wed, 11 Jul 2012 11:34:53 GMT
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2012/07/11
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With MVC3, I came over that problem where I was rendering a view with an updated model at the end of an HttpPost and the changes to the model were never applied to the rendered view :
public ActionResult Edit(JobModel editedJobModel)
{
// Update some model property
editedJobModel.IsActive = true;
// The view will NOT be updated as expected
return View(editedJobModel);
}
This is the standard behavior. In MVC3, POSTing the model does not render the Html helpers again. In my example, a HiddenFor bound to the IsActive value will not have its value set to true after the view is rendered.
Are you stuck, then ?
Well, for one, you’re not supposed to do that: in an ideal world you are supposed to apply the Post/Redirect/Get pattern. You would redirect to a new GET after your POST performed its actions. That’s what I usually do, but sometimes, when maintaining code and implementing slight changes to a pre-existing and tested logic, one prefers to keep structural changes to a minimum.
If you really have to (but my advice is to try to implement the PRG pattern whenever possible), here is a solution to alter values of the model on a POST and have the MVC engine render it correctly :
public ActionResult Edit(JobModel editedJobModel)
{
// NOT WORKING : Update some model property
//editedJobModel.IsActive = true;
//Force ModelState value for IsActive property
ModelState["IsActive"].Value = new ValueProviderResult(true, "True", null);
// The view will be updated as expected
return View(editedJobModel);
}
As you can see, it is a “dirty” solution, as the name (as a string) of the updated property is used as a key of the ModelState dictionary.
Also, the use of ValueProviderResult is not that straightforward.
But hey, it works.
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