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Home Interviews What is the difference between TempData, ViewData, and ViewBag? – MindStick
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1 Answers

ICSM Computer
ICSM Computer 12 Jun 2025
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In ASP.NET MVC, TempData, ViewData, and ViewBag are used to pass data from controllers to views, but they differ in lifetime, usage, and behavior.

Quick Comparison Table

Feature ViewData ViewBag TempData
Type Dictionary<string, object> Dynamic (wraps ViewData) TempDataDictionary (string keys)
Lifetime Current request only Current request only Survives redirect (one request)
Purpose Pass data to view Same as ViewData, more concise Pass data across requests (e.g. after redirect)
Syntax ViewData["Name"] ViewBag.Name TempData["Name"]
Null safety Prone to key typos Prone to runtime errors Same
Use case Any type of view data Simpler syntax for view data One-time messages, redirects

Detailed Breakdown

ViewData

  • Dictionary-like object (ViewDataDictionary)
  • Available only during the current HTTP request
  • Requires type casting and string keys
// Controller
ViewData["Message"] = "Hello from ViewData";

// View
<h2>@ViewData["Message"]</h2>

ViewBag

  • Syntactic sugar over ViewData using dynamic
  • Cleaner and avoids casting, but less safe at compile time
  • Also available only during the current request
// Controller
ViewBag.Message = "Hello from ViewBag";

// View
<h2>@ViewBag.Message</h2>

TempData

  • Stores data until it is read (or next request ends)
  • Survives a redirect (RedirectToAction)
  • Backed by Session — so session must be enabled
// Controller
TempData["SuccessMessage"] = "Profile updated successfully";
return RedirectToAction("Index");

// In redirected view
@if (TempData["SuccessMessage"] != null)
{
    <div>@TempData["SuccessMessage"]</div>
}

When to Use What?

Scenario Use
Pass data to view within same request ViewBag or ViewData
Share data between controller and view ViewBag or ViewData
Pass one-time messages (after redirect) TempData
Maintain small data across requests TempData
Store model or large objects Use ViewModel instead

Tip: Reuse ViewBag/ViewData with Partial Views

Both ViewBag and ViewData are passed automatically to partial views:

@Html.Partial("_MyPartial", model) // gets the ViewData and ViewBag

Pitfalls

  • ViewBag/ViewData are not type-safe – you can mistype the key or use wrong casting.
  • TempData gets cleared after one request unless you use TempData.Keep().
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