What s the difference between ViewData and ViewBag

Question

I saw the ViewBag in MVC 3  How s that different than ViewData in MVC 2

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ViewData  ViewData is used to pass data from controller to viewIt is derived from ViewDataDictionary classIt is available for the current request onlyRequires typecasting for complex data type and checks for null values to     avoid errorIf redirection occurs  then its value becomes null  ViewBag  ViewBag is also used to pass data from the controller to the respective viewViewBag is a dynamic property that takes advantage of the new dynamic      features in C  4 0It is also available for the current request onlyIf redirection occurs  then its value becomes nullDoesn   t require typecasting for complex data type

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It uses the C  4 0 dynamic feature  It achieves the same goal as viewdata and should be avoided in favor of using strongly typed view models  the same way as viewdata should be avoided    So basically it replaces magic strings   ViewData  Foo     with magic properties   ViewBag Foo   for which you have no compile time safety   I continue to blame Microsoft for ever introducing this concept in MVC   The name of the properties are case sensitive

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Although you might not have a technical advantage to choosing one format over the other  you should be aware of some important differences between the two syntaxes  One obvious difference is that ViewBag works only when the key you   re accessing is a valid C  identifi er  For example  if you place a value in ViewData  Key With Spaces    you can   t access that value using ViewBag because the code won   t compile  Another key issue to consider is that you cannot pass in dynamic values as parameters to extension methods  The C  compiler must know the real type of every parameter at compile time in order to choose the correct extension method  If any parameter is dynamic  compilation will fail  For example  this code will always fail   Html TextBox  name   ViewBag Name   To work around this  either use ViewData  Name   or cast the va

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ViewBag vs ViewData in MVC  http   royalarun blogspot in 2013 08 viewbag-viewdata-tempdata-and-view html  Similarities between ViewBag  amp  ViewData       Helps to maintain data when you move from controller to view  Used to   pass data from controller to corresponding view  Short life means   value becomes null when redirection occurs  This is because their goal   is to provide a way to communicate between controllers and views  It   s   a communication mechanism within the server call    Difference between ViewBag  amp  ViewData      ViewData is a dictionary of objects that is derived from   ViewDataDictionary class and accessible using strings as keys  ViewBag   is a dynamic property that takes advantage of the new dynamic features   in C  4 0  ViewData requires typecasting for complex data type and   check for null values to avoid error  ViewBag doesn   t require   typecasting for complex data type    ViewBag  amp  ViewData Example   public ActionResult Index            ViewBag Name    Arun Prakash          return View       public ActionResult Index           ViewData  Name      Arun Prakash         return View           Calling in View   ViewBag Name      ViewData  Name

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There are some subtle differences that mean you can use ViewData and ViewBag in slightly different ways from the view   One advantage is outlined in this post http   weblogs asp net hajan archive 2010 12 11 viewbag-dynamic-in-asp-net-mvc-3-rc-2 aspx and shows that casting can be avoided in the example by using the ViewBag instead of ViewData

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viewdata  is a dictionary used to store data between View and controller   u need to cast the view data object to its corresponding model  in the view to be able to retrieve data from it      ViewBag  is a dynamic property similar in its working to the view data  However it is better cuz it doesn t need to be casted to its corressponding model before using it in the view

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ViewBag and ViewData are two means which are used to pass information from controller to view in ASP Net MVC  The goal of using both mechanism is to provide the communicaton between controller and View  Both have short life that is the value of both becomes null once the redirection has occured ie  once the page has redirected from the source page  where we set the value of ViewBag or ViewData  to the target page   both ViewBag as well as ViewData becomes null   Despite having these similarities both  ViewBag and ViewData  are two different things if we talk about the implementation of both  The differences are as follows    1   If we analyse both implementation wise then we will find that ViewData is a dictionary data structure - Dictionary of Objects derived from ViewDataDictionary and accessible using strings as Keys to these values while ViewBag makes use of the dynamic features introduced in C 4 0 and is a dynamic property   2   While accessing the values form ViewData   we need to typecast the values  datatypes  as they are stored as Objects in the ViewData dictionary but there is no such need if we are accessing th value in case of ViewBag   3   In ViewBag we can set the value like this           ViewBag Name    Value      and can access as follows              ViewBag Name   While in case of ViewData the values can be set and accessed as follows       Setting ViewData as follows     ViewData  Name      Value     and accessing value like this    ViewData  Name      For more details click here

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In this way we can make it use the values to the pass the information between the controller to other page with TEMP DATA

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ViewData   It requires type casting for complex data types and checks for null values to avoid errors   ViewBag  It doesn   t require type casting for complex data types   Consider the following example    public class HomeController   Controller       public ActionResult Index                 var emp   new Employee                       EmpID 101              Name    Deepak               Salary   35000              Address    Delhi                      ViewData  emp     emp          ViewBag Employee   emp           return View               And the code for View is as follows    model MyProject Models EmpModel       Layout      Views Shared  Layout cshtml     ViewBag Title    Welcome to Home Page    var viewDataEmployee   ViewData  emp   as Employee    need type casting     lt h2 gt Welcome to Home Page lt  h2 gt  This Year Best Employee is   lt h4 gt  ViewBag Employee Name lt  h4 gt   lt h3 gt  viewDataEmployee Name lt  h3 gt

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Below is the point to point difference about ViewData  ViewBag  TempData  amp  Session  Credit copied askforprogram in   Follow the link for code example that i haven t mentioned here    ViewData in MVC   ViewData is property of ControllerBase class  ViewData is a type of dictionary object  ViewData is key-value dictionary collection  ViewData was introduced in MVC 1 0 version  ViewData works with  Net framework 3 5 and above  Need to do type conversion of code while enumerating  ViewData object keeps data only for current request   ViewBag in MVC   ViewBag is property of ControllerBase class  ViewBag is a type of dynamic object  ViewBag is a type of object  ViewBag was introduced in MVC 3 0 version  ViewBag works with  Net framework 4 0 and above  ViewBag uses property and handles it  so no need to do type conversion while  enumerating  ViewBag object keeps data only for current request   TempData in MVC   TempData is property of ControllerBase class  TempData is a type of dictionary object  TempData is key-value dictionary collection  TempData was introduced in MVC 1 0 version  TempData works with  Net framework 3 5 and above  Need to do type conversion of code while enumerating  TempData object is used to data between current request and subsequent request   Session in MVC   Session is property of Controller Abstract Class   Session is a type of HttpSessionStateBase  Session is key-value dictionary collection  Session was introduced in MVC 1 0 version  TempData works with  Net framework 1 0 and above  Need to do type conversion of code while enumerating  Session object keeps data for all requests  Valid for all requests  never expires

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Can I recommend to you to not use either   If you want to  send  data to your screen  send a strongly typed object  A K A  ViewModel  because it s easier to test   If you bind to some sort of  Model  and have random  viewbag  or  viewdata  items then it makes automated testing very difficult   If you are using these consider how you might be able to restructure and just use ViewModels

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All answers suggest that ViewBag and or ViewData is to pass data from Controller to Views which is misinformation  both are very useful to pass data from Views to Layout or Partial to Views  or ViewComponents  etc  It s not controller exclusive   as the default asp net sample have this in the layout page    lt title gt  ViewData  Title   - MyApp lt  title gt    and in any view  ViewData  Title      Details     So then  to asking the question   what s the difference between ViewBag and ViewData    The most notable difference is ViewData is a Strongly Typed Dictionary while ViewBag is a dynamic type    Note that the data inside IS THE SAME  ViewData  Title      MyTitle   ViewBag Title     returns  MyTitle     When to use one or another    ViewBag doesn t support not valid C  names  you can t access ViewData  Key With Space   with ViewBag ViewBag Something is dynamic and you may have problems when calling methods  like extension methods  that needs to know the exact parameter at compile time  ViewBag can check for nulls syntactical cleaner  ViewBag Person  Name ViewData have all the properties of a Dictionary like ContainsKey  Add  etc  so you can use ViewData Add  somekey    somevalue   keep in mind it might throw exceptions  Using ViewData on views needs TypeCasting while ViewBag don t    Knowing the subtle differences  using one or another is much more a taste preference   Normally you can think of ViewBag AnyKey to an alias of ViewData  AnyKey

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One main difference I noticed between ViewData and ViewBag is   ViewData   it will return object does not matter what you have assigned into this and need to typecast again back to the original type   ViewBag   it is enough smart to return exact type what you have assigned to it it does not matter weather you have assigned simple type  i e  int  string etc   or complex type   Ex  Controller code    namespace WebApplication1 Controllers       public class HomeController   Controller               public ActionResult Index                         Products p1   new Products                p1 productId   101              p1 productName    Phone               Products p2   new Products                p2 productId   102              p2 productName    laptop                List lt Products gt  products   new List lt Products gt                 products Add p1               products Add p2               ViewBag Countries   products              return View                        public class Products               public int productId   get  set            public string productName   get  set              View Code    lt ul gt               foreach  WebApplication1 Controllers Products item in ViewBag Countries                             lt li gt  item productId  amp nbsp  amp nbsp  amp nbsp  item productName lt  li gt                         lt  ul gt    OutPut Screen

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Here ViewData and ViewBag both are used pass data from Controller to View   1  ViewData   -- ViewData is dictionary object that is derived from ViewDataDictonary class   -- Data only allow for one request  ViewData values get cleared when page redirecting occurs   -- ViewData value must be typed cate before use   Example   In Controller  public ActionResult PassingDatatoViewWithViewData           ViewData  Message      This message shown in view with the ViewData         return View        In View   ViewData  Message      -- With ViewData is a pair like Key and Value  Message is Key and in inverted comma value is Value   -- Data is simple so we can not use typecasting here if data is complex then using type casting   public ActionResult PassingDatatoViewWithViewData           var type  new List lt string gt                 MVC            MVP            MVVC             ViewData  types     type      return View        -- In View data  can be extracted as   lt ul gt           foreach  var items in  List lt string gt  ViewData  types                        lt li gt  items lt  li gt               lt  ul gt    2  ViewBag  --ViewBag uses the dynamic feature ViewBag wrapper around the ViewData   -- In ViewBag type casting is required   -- Same as ViewData  if redirection occurs value becomes null   Example    public ActionResult PassingDatatoViewWithViewBag               ViewData Message    This message shown in view with the ViewBag             return View        In View   ViewBag vbMessage   --For Complex type use ViewBag  public ActionResult PassingDatatoViewWithViewBag               var type  new List lt string gt                         MVC                MVP                MVVC                     ViewBag types   type          return View         -- In View data can be extracted as   lt ul gt          foreach  var items in ViewBag types                     lt li gt  items lt  li gt            lt  ul gt    -- the main difference is that ViewBag not required typecasting but ViewData is required typecasting

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public ActionResult Index         ViewBag Name    Monjurul Habib       return View       public ActionResult Index         ViewData  Name      Monjurul Habib       return View        In View    ViewBag Name   ViewData  Name

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Internally ViewBag properties are stored as name value pairs in the ViewData dictionary    Note  in most pre-release versions of MVC 3  the ViewBag property was named the ViewModel as noted in this snippet from MVC 3 release notes    edited 10-8-12  It was suggested I post the source of this info I posted  here is the source   http   www asp net whitepapers mvc3-release-notes  Toc2 4     MVC 2 controllers support a ViewData   property that enables you to pass data   to a view template using a late-bound   dictionary API  In MVC 3  you can also   use somewhat simpler syntax with the   ViewBag property to accomplish the   same purpose  For example  instead of   writing ViewData  Message    text     you can write ViewBag Message  text     You do not need to define any   strongly-typed classes to use the   ViewBag property  Because it is a   dynamic property  you can instead just   get or set properties and it will   resolve them dynamically at run time    Internally  ViewBag properties are   stored as name value pairs in the   ViewData dictionary   Note  in most   pre-release versions of MVC 3  the   ViewBag property was named the   ViewModel property

[.net] What's the difference between ViewData and ViewBag?

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