Using <%$ %> in ASP.NET MVC

Question

In ASP.NET WebForms you can reference appSettings directly in your markup with this syntax:

<%$ MySettingKey %>

Unfortunately this does not work in ASP.NET MVC because, as MSDN points out, this syntax only works in server controls.

I've run into a few situations where I would love to use this syntactic sugar in an ASP.NET MVC view (WebFormsViewEngine). Does anyone know if there is a way to get this working?

Seems like we might be able to derive from WebFormsViewEngine and add this as a feature, perhaps?

Answer 1

In my memories, <%$ %> tag reference to globalzation resources, am I wrong?

Answer 2

Not very clean but in an ASP.NET MVC View you could actually write this:

<asp:Literal ID="dummy" runat="server" Text="<%$appSettings:MySettingKey%>" />

Which will effectively print whatever the value you have in appSettings:

<appSettings>
    <add key="MySettingKey" value="SOME VALUE"/>
</appSettings>

Oh and there won't be a VIEWSTATE tag added to your page :-)

Now to the point: I will strongly discourage you doing something like this MVC. It is not the View's responsibility to pull the data to show, it's the controller that needs to pass it. So I would make MySetting a property of the ViewModel which will be populated by the controller and passed to the view to be shown.

public ActionResult Index()
{
    var model = new SomeViewModel
    {
        // TODO: Might consider some repository here
        MySetting = ConfigurationManager.AppSettings["MySetting"]
    }
    return View(model);
}

And in the View:

<%= Html.Encode(Model.MySetting) %>

or even shorter with the new syntax introduced in ASP.NET 4:

<%: Model.MySetting %>

---

UPDATE:

Yet another alternative if you think that MySetting is not a property of the ViewModel (like some css name or similar) you could extend the HtmlHelper:

public static string ConfigValue(this HtmlHelper htmlHelper, string key)
{
    return ConfigurationManager.AppSettings[key];
}

And use it like this:

<%= Html.Encode(Html.ConfigValue("MySetting")) %>

Answer 3

It still works with server controls in MVC, so no one's stopping you from writing a simple control which will just print out the key.

Answer 4

I prefer to have something like an ApplicationFacade. This is something I picked up from Mark Dickinson when we worked together.

The premise is very similar to what Darin is proposing, except it is strongly typed...

public static class ApplicationFacade
{
  public static string MySetting
  {
    get
    {
      return ConfigValue("MySetting");
    }
  }

  //A bool!
  public static bool IsWebsiteLive
  {
    get
    {
      return (bool)ConfigValue("IsWebsiteLive");
    }
  }

  private static string ConfigValue(string key)
  {
    return ConfigurationManager.AppSettings[key];
  }
}

Then you would call it in your view thus:

<%= ApplicationFacade.MySetting %>