What is TempData property in MVC2

In this article we will see what is the use of TempData property in MVC2.

The TempData property is used to pass data between different action methods in MVC2. In some cases an ActionMethod might need to pass data to another Action Method.

Every controller maintains a "TempDataDictionary" object which can be used
to store data before it calls another action method using its RedirectToAction method. The method that is being called can now use
the value from this "TempDataDictionary" object because this value is stored in session state. The TempData value persists either till the session times out or untill it is read. The value in TempData is persisted across multiple requests.

Below example shows a data class that is used to rectify an error and to pass the data between actions.

public class ErrorInfo
{
    public string ErrorMessage { get; set; }
    public string EmpName{ get; set; }
}


public class EmployeeController
{
 ...
public ActionResult InsertEmployee(string empName)
{
    if (String.IsNullOrEmpty(empName))
    {
        ErrorInfo errorInfo = new ErrorInfo();
        errorInfo.ErrorMessage = "Please provide Employee Name";
        errorInfo.EmpName = empName;
        TempData["error"] = errorInfo;
        return RedirectToAction("NewEmployee");
    }
    // In case of no errors
    ...
    return View();
}

public ActionResult NewEmployee()
{
    ErrorInfo err = TempData["error"] as ErrorInfo;
    if (err != null)
    {
   // If the previous action resulted in an error,capture it for display.
        ViewData["EmpName"] = err.EmpName;
        ViewData["ErrorMessage"] = err.ErrorMessage;
    }
       return View();
}

  <% if (ViewData["ErrorMessage"] != null) { %>
    Error while inserting the Employee Information  for 
   <%=ViewData["EmpName"] %> :
    <br />
    <%= ViewData["ErrorMessage"] %>
    <br />
  <% } %>