Role based authentication feed back to user in ASP.NET MVC

I am using role based Authentication for some of the features in my ASP.NET MVC application by implementing

<Authorize(Roles:="Administrator")> _
 Function AdminPage() As ActionResult
    Return View()
  End Function

If the user is not logged in as Administrator this will redirect the user to login page but there is no feed back why it did that. So I want to display a message li开发者_StackOverflow中文版ke "You must be administrator to access this feature."

I am looking for a clean way to do this.

Thank in advance.

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You could easily achieve this by writing a custom authorize attribute:

Public Class CustomAuthorizeAttribute
    Inherits AuthorizeAttribute
    Protected Overrides Sub HandleUnauthorizedRequest(filterContext As AuthorizationContext)
        MyBase.HandleUnauthorizedRequest(filterContext)
        filterContext.Controller.TempData("message") = String.Format("You need to be {0} to access this resource", Me.Roles)
    End Sub
End Class

And then decorate the controller action with this custom attribute:

<CustomAuthorize(Roles := "Administrator")> _
Public Function AdminPage() As ActionResult
    Return View()
End Function

And somewhere on your Logon View:

<div><%: TempData("message") %></div>