Access Viewbag property on all views

Question

How can I access some ViewBag properties across all my views? I want to have some information like current user name, etc accessible everywhere, but without having to to specifically define the properties in each ActionResult method on my project

Answer 1

The best and straight forward way to accomplish your requirement is to make a Custom Base Controller and inherit your Controller from this Base Controller.

public class MyBaseController : Controller
{
    protected override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        ViewBag.someThing = "someThing"; //Add whatever
        base.OnActionExecuting(filterContext);
    }
}

Now instead of inheriting Controller class,inherit MyBaseController in your Controller as shown :-

public class MyOtherController : MyBaseController 
{
    public ActionResult MyOtherAction()
    {
       //Your Stuff
       return View();
    }
    //Other ActionResults
}

Answer 2

You can achieve what you want in a number of ways, each one with their pros and cons.

1. With a Base Class

public class BaseController : Controller
{
    protected override ViewResult View(IView view, object model)
    {
        this.ViewBag.MyProperty = "value";
        return base.View(view, model);
    }
}

PROS: Quite simple to implement, few lines of code, highly reusable, can be opted-out at will (see comments below).

CONS: Being forced to derive all your controllers from a base class might have some impact, especially if you have a lot of controllers already in place and/or you need to derive them from other base classes.

2. With a Module

public class ViewBagPropertyModule: Module
{
    protected override void AttachToComponentRegistration(IComponentRegistry cr,
                                                  IComponentRegistration reg)
    {
        Type limitType = reg.Activator.LimitType;
        if (typeof(Controller).IsAssignableFrom(limitType))
        {
            registration.Activated += (s, e) =>
            {
                dynamic viewBag = ((Controller)e.Instance).ViewBag;
                viewBag.MyProperty= "value";
            };
        }
    }
}

PROS: None I’m aware of.

CONS: None I’m aware of (except being a bit counterintuitive).

3. With a RegisterController Hook

builder.RegisterControllers(asm)
    .OnActivated(e => {
        dynamic viewBag = ((Controller)e.Instance).ViewBag;
        viewBag.MyProperty = "value";
    });

PROS: Fast, secure, reusable: ideal for any IoC design pattern.

CONS: Not always suited for small project and/or simple websites: if you’re not using IoC you’re often not using RegisterController at all.

4. With an ActionFilter attribute

public class MyPropertyActionFilter : ActionFilterAttribute
{
    public override void OnResultExecuting(ResultExecutingContext filterContext)
    {
        filterContext.Controller.ViewBag.MyProperty = "value";
    }
}

and then in your Global.asax.cs file:

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    GlobalFilters.Filters.Add(new MyPropertyActionFilter(), 0);
}

PROS: Easily the less-obtrusive method amongst those mentioned.

CONS: None I’m aware of.

I also wrote this article on my blog explaining all the above methods.

Answer 3

One way: Create a custom attribute, then you can apply it globally in the FilterConfig. Then you don't have to do anything in your controllers.

public class MyCustomViewActionFilter : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        dynamic ViewBag = filterContext.Controller.ViewBag;

        ViewBag.Id = "123";
        ViewBag.Name = "Bob";
    }
}

In App_Start/FilterConfig.cs:

    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        filters.Add(new MyCustomViewActionFilter());
    }

Another way if all you need is the User information. You can add the following to the top of your view:

@using Microsoft.AspNet.Identity

Then access your User Name using the following syntax:

@User.Identity.GetUserName()

You can also override the IPrincipal implementation and provide your own properties and methods to add more information you need to render.

UPDATE: looking at MVC 6 in Asp.Net vNext this is actually baked into the framework. http://www.asp.net/vnext/overview/aspnet-vnext/vc#inj