TempData stores the data temporarily and automatically removes it after retrieving a value.

TempData is used to transfer data from view to controller, controller to view, or from one action method to another action method of the same or a different controller.TempData is a property in the ControllerBase class. So, it is available in any controller or view in the ASP.NET MVC application.

Explaination of TempData, keep() and peek()

When an object in a TempDataDictionary is read, it will be marked for deletion at the end of that request. That means if you put something on TempData like TempData["value"] = "DotNet Palace";
And on another request you access it, the value will be there but as soon as you read it, the value will be marked for deletion:
//second request, read value and is marked for deletion
object value = TempData["value"]; //third request, value is not there as it was deleted at the end of the second request
TempData["value"] == null

The Peek and Keep methods allow you to read the value without marking it for deletion. Say we get back to the first request where the value was saved to TempData. With Peek you get the value without marking it for deletion with a single call,

//second request, PEEK value so it is not deleted at the end of the request
object value = TempData.Peek("value");
//third request, read value and mark it for deletion
object value = TempData["value"];

With Keep you specify a key that was marked for deletion that you want to keep. Retrieving the object and later on saving it from deletion are 2 different calls.

//second request, get value marking it from deletion
object value = TempData["value"];
//later on decide to keep it
TempData.Keep("value");
//third request, read value and mark it for deletion
object value = TempData["value"];

You can use Peek when you always want to retain the value for another request. Use Keep when retaining the value depends on additional logic.

More Explaination of TempData, keep() and peek()

Condition 1 (Not read) If you set a “TempData” inside your action and if you do not read it in your view then “TempData” will be persisted for the next request.

Condition 2 (Normal Read) If you read the “TempData” normally like the below code it will not persist for the next request.
string str = TempData["MyData"];
Even if you are displaying it’s a normal read like the code below.
@TempData["MyData"];

Condition 3 (Read and Keep) If you read the “TempData” and call the “Keep” method it will be persisted. @TempData["MyData"];
TempData.Keep("MyData");


Condition 4 ( Peek and Read) If you read “TempData” by using the “Peek” method it will persist for the next request. string str = TempData.Peek("Td").ToString();