Passing a variable from [HttpPost] method to [HttpGet] method
I am redirecting the view from [HttpPost] method to [HttpGet] method. I have gotten it to work, but want to know if this is the best way to do this.
Here is my code:
[HttpPost]
public ActionResult SubmitStudent()
{
StudentViewModel model = TempData["model"] as StudentResponseViewModel;
TempData["id"] = model.Id;
TempData["name"] = model.Name;
return RedirectToAction("DisplayStudent");
}
[HttpGet]
public ActionResult DisplayStudent()
{
ViewData["id"] = TempData["id"];
ViewData["name"] = TempData["name"];
return View();
}
View:
<%@ Page
Language="C#"
Inherits="System.Web.Mvc.ViewPage"
%>
<html>
<head runat="server">
<title>DisplayStudent</title>
</head>
<body>
<div>
<%= ViewData["id"]%> <br />
<%= ViewData["name"]%>
</div>
</body>
</html>
Answer
There are basically 3 techniques in ASP.NET MVC to implement the PRG pattern.
- TempData
Using TempData is indeed one way of passing information for a single redirect. The drawback I see with this approach is that if the user hits F5 on the final redirected page he will no longer be able to fetch the data as it will be removed from TempData for subsequent requests:
[HttpPost]
public ActionResult SubmitStudent(StudentResponseViewModel model)
{
if (!ModelState.IsValid)
{
// The user did some mistakes when filling the form => redisplay it
return View(model);
}
// TODO: the model is valid => do some processing on it
TempData["model"] = model;
return RedirectToAction("DisplayStudent");
}
[HttpGet]
public ActionResult DisplayStudent()
{
var model = TempData["model"] as StudentResponseViewModel;
return View(model);
}
- Query string parameters
Another approach if you don't have many data to send is to send them as query string parameters, like this:
[HttpPost]
public ActionResult SubmitStudent(StudentResponseViewModel model)
{
if (!ModelState.IsValid)
{
// The user did some mistakes when filling the form => redisplay it
return View(model);
}
// TODO: the model is valid => do some processing on it
// redirect by passing the properties of the model as query string parameters
return RedirectToAction("DisplayStudent", new
{
Id = model.Id,
Name = model.Name
});
}
[HttpGet]
public ActionResult DisplayStudent(StudentResponseViewModel model)
{
return View(model);
}
- Persistence
Yet another approach and IMHO the best consists into persisting this model into some data store (like a database or something and then when you want to redirect to the GET action send only an id allowing for it to fetch the model from wherever you persisted it). Here's the pattern:
[HttpPost]
public ActionResult SubmitStudent(StudentResponseViewModel model)
{
if (!ModelState.IsValid)
{
// The user did some mistakes when filling the form => redisplay it
return View(model);
}
// TODO: the model is valid => do some processing on it
// persist the model
int id = PersistTheModel(model);
// redirect by passing the properties of the model as query string parameters
return RedirectToAction("DisplayStudent", new { Id = id });
}
[HttpGet]
public ActionResult DisplayStudent(int id)
{
StudentResponseViewModel model = FetchTheModelFromSomewhere(id);
return View(model);
}
Each method has its pros and cons. Up to you to choose which one suits best to your scenario.