1. TempData is meant to be a very short-lived instance, and you should only use it
during the current and the subsequent requests only.
2. Since TempData works this way, you need to know for sure what the next request will be, and
redirecting to another view is the only time you can guarantee this.
3. Therefore, the only scenario where using TempData will reliably work is when
you are redirecting.This is because a redirect kills the current request , then creates a
new request on the server to serve the redirected view.
4. Simply said, Asp.Net MVC TempData dictionary is used to share data between
controller actions.
5. The value of TempData persists until it is read or until the current user’s session times out.
6. By default, the TempData saves its content to the session state.
7. TempData values are marked for deletion when you read them. At the end of the request,
any marked values are deleted.
8. The benefit is that if you have a chain of multiple redirections it won’t cause TempData to
be emptied the values will still be there until you actually use them, then they clear up after
themselves automatically.
How to use TempData ?
Best Way
There are 2 ways which we can use TempData.
Method 1 :
We can use it Inside the Redirect Action method like below.
Model
public class CreditCardInfo
{
public string CardNumber { get; set; }
public string Span { get; set; }
public int ExpiryMonth { get; set; }
}
Action Methods
TempData Declared Action Method
[HttpPost]
public ActionResult CreateOwnerCreditCardPayments(CreditCard cc, FormCollection frm)
{
var providerKey = frm["providerKey"];
var creditCardInfo = new CreditCardInfo();
creditCardInfo.CardNumber = cc.Number;
creditCardInfo.ExpiryMonth = cc.ExpMonth;
creditCardInfo.Span = cc.Span;
//persist data for next request
TempData["CreditCardInfo"] = creditCardInfo;
return RedirectToAction("CreditCardPayment", new { providerKey = providerKey});
}
TempData Used Action Method
[HttpGet]
public ActionResult CreditCardPayment(string providerKey)
{
if (TempData["CreditCardInfo"] != null)
{
var creditCardInfo = TempData["CreditCardInfo"] as CreditCardInfo;
var payPros =(PayPros)PaymentGateway.GetPayment(Enums.PayPros);
var creditCardResponse = payPros.Ecommerce(creditCardInfo);
return View();
}
else
{
return View("error");
}
}
Method 2 :
You can use TempData Inside a Redirected Action Method's View.
In our example it is :
CreditCardPayment.cshtml - View.
@{
if (TempData["CreditCardInfo"] != null)
{
var creditCardInfo = TempData["CreditCardInfo"] as CreditCardInfo;
}
}
Good Practice : Always do null check and do necessary action if TempData is null
(either get data again or exit gracefully).
Bad Way of using TempData
When using with ViewResult Action method.
[HttpPost]
public ActionResult CreateOwnerCreditCardPayments(CreditCard cc, FormCollection frm)
{
var providerKey = frm["providerKey"];
var creditCardInfo = new CreditCardInfo();
creditCardInfo.CardNumber = cc.Number;
creditCardInfo.ExpiryMonth = cc.ExpMonth;
creditCardInfo.Span = cc.Span;
//persist data
TempData["CreditCardInfo"] = creditCardInfo;
return View();
}
View
Related View :
CreateOwnerCreditCardPayments.cshtml - View
@{
if (TempData["CreditCardInfo"] != null)
{
var creditCardInfo = TempData["CreditCardInfo"] as CreditCardInfo;
}
}
Why this Method is Bad ?
If your controller action returns a ViewResult, and you are tempted to put data into TempData,
Don’t do That.Use ViewData/ViewBag, instead, in this case.
TempData is meant to be a very short-lived instance, and you should only use it during the current and the subsequent requests only. Since TempData works this way, you need to know for sure what the next request will be, and Redirecting to another View is the only time you can guarantee this.Therefore, the only scenario where using TempData will Reliably work is when you are Redirecting.So Keep in Mind.
Other Usage of TempData
Usage 1 : If you want to keep TempData values even after reading them call Keep().Then those
values will keep for next request also.
TempData.Keep("CreditCardInfo");
Usage 2 : If you want to remove TempData values then call Remove().Then those values
will remove from current and next request.
Conclusion
TempData, is geared specifically for working with data on HTTP redirects, so remember to be
cautious when using TempData. Always do null check before use TempData.
If you set the Session State Mode to Out of Process , then the data (model) you put in it must be
Serializable. (Use [Serializable] attribute)
What is the meaning of 'Session State Mode to Out of Process' ?
Such as State Server mode, which stores session state in a separate process called the
ASP.NET state service. This ensures that session state is preserved if the Web
application is restarted and also makes session state available to multiple Web servers in a
Web farm or Windows Azure (Cloud) environment.
I hope this helps to You.Comments and feedback greatly appreciated.
Happy Coding.
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