How to expose global object like @User in razor views?

Question

How/Where can I declare an object like @User so that it can be referenced globally in any razor view using @?

Something similar to:

_LoginPartial.cshtml:

@if(Request.IsAuthenticated) {
    <text>Signed In As  <strong>@User.Identity.Name</strong> |

but instead reference my object:

  @if(this && that) { <text>@MyObject.GetData</text> }

Answer 1

You can change the base type of a Razor page to a one of your own eg:

public class UserAwareViewPage : System.Web.Mvc.WebViewPage
{
  public IPrincipal User { get { return Thread.CurrentPrincipal; } }
}

And then modify your config file like so:

<system.web.webPages.razor>
  <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, 
  System.Web.Mvc, Version=3.0.0.0, 
  Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
  <pages pageBaseType="Your.Namespace.UserAwareViewPage">
    <namespaces>
      <add namespace="System.Web.Mvc" />
      <add namespace="System.Web.Mvc.Ajax" />
      <add namespace="System.Web.Mvc.Html" />
      <add namespace="System.Web.Routing" />
    </namespaces>
  </pages>
</system.web.webPages.razor>

Phil Haack has a very good blog post on this here.

Alternatively, you can add an extension method to System.Web.Mvc.WebViewPage (the base type for razor pages) and use this.

public static IPrincipal User(this System.Web.Mvc.WebViewPage page)
{
  return Thread.CurrentPrincipal;
}

Which would be useable like so:

@if(Request.IsAuthenticated) {
<text>Signed In As  <strong>@User().Identity.Name</strong>

Personally, I prefer the first approach, but thought I'd provide the second for an alternative option.

Answer 2

The @ syntax isn't referencing values in any way, it's just telling the view engine that you're beginning a server-side code block.

There's nothing "global" about it. In this case, User is a property on the System.Web.WebPages.WebPageRenderingBase abstract class, which is used by the view engine when rendering views as they inherit from it.

I suppose you can extend the WebViewPage or the WebViewPage<> classes to add properties to them. There may be a better way to achieve what you're trying to do without modifying those, though. If you're trying to pass data to the View, shouldn't that data be part of the ViewModel?

Ideally you'd supply everything the View needs in a custom ViewModel and the View would inherit from WebViewPage<CustomViewModel>.

In Razor syntax I think you'd begin the CSHTML with something like:

@model CustomViewModel

Then you'd access properties on that using the Model property:

@Model.SomeProperty