MVC 6 @inherit RazorPage

Question

I am trying to migrate an MVC 5 Application to ASP.NET 5 MVC 6 (Beta 7). Having problems when using the @inherits and @model directive together. Works fine when they are used separately.

In my _ViewImports i added the @inherits directive to use a base page with some custom user properties.

public abstract class BaseViewPage<TModel> : RazorPage<TModel>
{
    protected MyPrincipal AppUser
    {
        get
        {
            return new MyPrincipal(this.User as ClaimsPrincipal);
        }
    }
}

_ViewImports.cshttml

@inherits CommonWeb.BaseViewPage<TModel>
@addTagHelper "*, Microsoft.AspNet.Mvc.TagHelpers"

And then i can go AppUser. in all my views. This works if i dont use a strongly typed view. If i add the @model directive in any view the inherited view page goes away.

Help appreciated

Update:

I did this successfully by using a custom pageBaseType in the web.config in prior versions.

Workaround.

public class ViewHelper
{
    ViewContext _context;

    public ViewHelper(ViewContext context)
    {
        _context = context;
    }

    public MyPrincipal AppUser
    {
        get
        {
            return new MyPrincipal(_context.HttpContext.User as ClaimsPrincipal);
        }
    }

    public string ControllerName
    {
        get
        {
            return _context.RouteData.Values["controller"].ToString();
        }
    }
}

View:

@{ var viewHelper = new ViewHelper(ViewContext);}

A way to achieve this for all views?

Answer 1

There is a better way in MVC 6, which now supports injecting dependencies on the views with the @inject directive. (The directive @inject IFoo Foo allows you to use in your view a property named Foo of type IFoo)

Create a new interface IAppUserAccessor for getting your app user, for example:

public interface IAppUserAccessor
{
    MyPrincipal GetAppUser();
}

Create a class AppUserAccessor implementing it:

public class AppUserAccessor : IAppUserAccessor
{
    private IHttpContextAccessor httpContextProvider;
    public AppUserAccessor(IHttpContextAccessor httpContextProvider)
    {
        this.httpContextProvider = httpContextProvider;
    }

    public MyPrincipal GetAppUser()
    {
        return new MyPrincipal (
                       httpContextProvider.HttpContext.User as ClaimsPrincipal);            
    }
}

Register the new interface in the services container by adding a new entry in the ConfigureServices method of Startup.cs:

services.AddTransient<IAppUserAccessor, AppUserAccessor>();

Finally use the @inject directive to inject the IAppUserAccessor in your views. If you add the directive in ViewImports.cshtml then it will be available on every view.

@inject WebApplication4.Services.IAppUserAccessor AppUserAccessor

With all the pieces above you can now just use it on your view(s):

@AppUserAccessor.GetAppUser()

Update

If you need to inspect the route values, like the controller name, you can inject an IActionContextAccessor into your class and use it as follows:

public AppUserAccessor(IHttpContextAccessor httpContextProvider, IActionContextAccessor actionContextAccessor)
{
    this.httpContextProvider = httpContextProvider;
    this.actionContextAccessor = actionContextAccessor;
}

...

public string ControllerName
{
    get { return actionContextAccessor.ActionContext.RouteData.Values["controller"].ToString(); }            
}

Of course, that doesn't look like an AppUserAccessor anymore and smells like it has different responsabilities. At the very least it needs a more appropriate name :)

I would double check what do I need the controller name for. There might be a better way to accomplish your objective. (For example, if you need it for generating new links/urls you might just use an IUrlHelper)

Accessing ViewContext

Looks like beta8 has added support for injecting the ViewContext, although the implementation details may change before RC. See this question