Asp.net 命名空间 ASP 中不存在 ASP.global_asax

I created a RazorFunctions.cshtml file on App_Code

@functions {
    public static string GetActiveClassIf(string controllerName, string actionName = null)
    {
        var routeData = @HttpContext.Current.Request.RequestContext.RouteData;
        string currentController = routeData.Values["controller"].ToString();
        string currentAction = routeData.Values["action"].ToString();
        return controllerName == currentController &&
            (String.IsNullOrEmpty(actionName) || currentAction == actionName) ? "active" : "";
    }
}

and when I compile, it give me 2 errors (compilation get success and site work without problem) but the errors are annoying.

The RazorFunctions.cshtml are as Content (tried compile but doesn't work with cshtml files of course)

Global.asax.cs is :

public class MvcApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        ModelMetadataConfig.RegisterModelMetadata();
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);
        Database.SetInitializer(new MigrateDatabaseToLatestVersion<ApplicationDbContext, Configuration>());
        //Database.SetInitializer(new DropCreateDatabaseAlways<ApplicationDbContext>());
    }
}

and

<%@ Application Codebehind="Global.asax.cs" Inherits="Bouron.Web.MvcApplication" Language="C#" %>

This is the first time I use the App_Code so I don't know what else to do, all search returns ASP.NET 1-2 results, are out of date where razor doesn't even exist so I'm not sure how can I solve this.

I'm using Visual Studio 2015 (just in case it matters)