[asp.net] How ViewBag in ASP.NET MVC works

How does the ASP.NET MVC's ViewBag work? MSDN says it is just an Object, which intrigues me, how does "Magic" properties such as ViewBag.Foo and magic strings ViewBag["Hello"] actually work?

Also, how can I make one and use it in my ASP.NET WebForms app?

Examples would be really appreciated!

This question is related to asp.net asp.net-mvc viewbag

The answer is

It's a dynamic object, meaning you can add properties to it in the controller, and read them later in the view, because you are essentially creating the object as you do, a feature of the dynamic type. See this MSDN article on dynamics. See this article on it's usage in relation to MVC.

If you wanted to use this for web forms, add a dynamic property to a base page class like so:

public class BasePage : Page

    public dynamic ViewBagProperty

Have all of your pages inherit from this. You should be able to, in your ASP.NET markup, do:

<%= ViewBagProperty.X %>

That should work. If not, there are ways to work around it.

public dynamic ViewBag
        if (_viewBag == null)
            _viewBag = new DynamicViewData(() => ViewData);

        return _viewBag;

ViewBag is a dynamic type that allow you to dynamically set or get values and allow you to add any number of additional fields without a strongly-typed class They allow you to pass data from controller to view. In controller......

public ActionResult Index()
    ViewBag.victor = "My name is Victor";
    return View();

In view

@foreach(string a in ViewBag.victor)

What I have learnt is that both should have the save dynamic name property ie ViewBag.victor

The ViewBag is an System.Dynamic.ExpandoObject as suggested. The properties in the ViewBag are essentially KeyValue pairs, where you access the value by the key. In this sense these are equivalent:

ViewBag.Foo = "Bar";
ViewBag["Foo"] = "Bar";

ViewBag is of type dynamic. More, you cannot do ViewBag["Foo"]. You will get exception - Cannot apply indexing with [] to an expression of type 'System.Dynamic.DynamicObject'.

Internal implementation of ViewBag actually stores Foo into ViewData["Foo"] (type of ViewDataDictionary), so those 2 are interchangeable. ViewData["Foo"] and ViewBag.Foo.

And scope. ViewBag and ViewData are ment to pass data between Controller's Actions and View it renders.

ViewBag is used to pass data from Controller Action to view to render the data that being passed. Now you can pass data using between Controller Action and View either by using ViewBag or ViewData. ViewBag: It is type of Dynamic object, that means you can add new fields to viewbag dynamically and access these fields in the View. You need to initialize the object of viewbag at the time of creating new fields.

e.g: 1. Creating ViewBag: ViewBag.FirstName="John";

  1. Accessing View: @ViewBag.FirstName.

Examples related to asp.net

RegisterStartupScript from code behind not working when Update Panel is used You must add a reference to assembly 'netstandard, Version= No authenticationScheme was specified, and there was no DefaultChallengeScheme found with default authentification and custom authorization How to use log4net in Asp.net core 2.0 Visual Studio 2017 error: Unable to start program, An operation is not legal in the current state How to create roles in ASP.NET Core and assign them to users? How to handle Uncaught (in promise) DOMException: The play() request was interrupted by a call to pause() ASP.NET Core Web API Authentication Could not load file or assembly 'CrystalDecisions.ReportAppServer.CommLayer, Version=13.0.2000.0 WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for jquery

Examples related to asp.net-mvc

Using Lato fonts in my css (@font-face) Better solution without exluding fields from Binding Vue.js get selected option on @change You must add a reference to assembly 'netstandard, Version= How to send json data in POST request using C# VS 2017 Metadata file '.dll could not be found The default XML namespace of the project must be the MSBuild XML namespace How to create roles in ASP.NET Core and assign them to users? The model item passed into the dictionary is of type .. but this dictionary requires a model item of type How to use npm with ASP.NET Core

Examples related to viewbag

Updating PartialView mvc 4 How to use a ViewBag to create a dropdownlist? How ViewBag in ASP.NET MVC works How to create own dynamic type or dynamic object in C#? Pass a simple string from controller to a view MVC3 How to display a list using ViewBag How do I access ViewBag from JS The name 'ViewBag' does not exist in the current context What's the difference between ViewData and ViewBag?