Automatically switching views for AMP in ASP.NET MVC - asp.net-core-mvc

Question

I want to create and AMP version of my website in ASP.NET MVC using .NET Core 2.0. Previously I had done some work with DisplayModeProvider instances in tha past on .Net framework, but that does not seem to be an option in .NET Core.
What I want to be able to do is alter the view names to be index.amp.cshtml rather than index.cshtml when my URL starts iwth /amp. What's the best way to achieve this in .NET Core?

Answer 1

You can do something like this using IViewLocationExpander. As it happens, I was playing with this a few days ago so I have some code samples to hand. If you create something like this:
public class AmpViewLocationExpander : IViewLocationExpander
{
public void PopulateValues(ViewLocationExpanderContext context)
{
var contains = context.ActionContext.HttpContext.Request.Query.ContainsKey("amp");
context.Values.Add("AmpKey", contains.ToString());
var containsStem = context.ActionContext.HttpContext.Request.Path.StartsWithSegments("/amp");
context.Values.Add("AmpStem", containsStem.ToString());
}
public IEnumerable<string> ExpandViewLocations(ViewLocationExpanderContext context, IEnumerable<string> viewLocations)
{
if (!(context.ActionContext.ActionDescriptor is ControllerActionDescriptor descriptor)) { return viewLocations; }
if (context.ActionContext.HttpContext.Request.Query.ContainsKey("amp")
|| context.ActionContext.HttpContext.Request.Path.StartsWithSegments("/amp")
)
{
return viewLocations.Select(x => x.Replace("{0}", "{0}.amp"));
}
return viewLocations;
}
}
iViewLocationExpander can be found in Microsoft.AspNetCore.Mvc.Razor
Then in your Configure Services method in Startup.cs, add the following:
services.Configure<RazorViewEngineOptions>(options =>
{
options.ViewLocationExpanders.Add(new AmpViewLocationExtender());
});
What this will do is update the view locations per request to insert .amp before .cshtml any time the URL either starts with /amp or there is a query string key of amp. If your AMP views don't exist, it might blow-up a little, I've not fully tested it, but it should get you started.

Answer 2

You can define this Middleware :
public class AmpMiddleware
{
private RequestDelegate _next;
public AmpMiddleware(RequestDelegate next)
{
_next = next;
}
public Task Invoke(HttpContext context)
{
const string ampTag = "/amp";
var path = context.Request.Path;
if (path.HasValue)
{
var ampPos = path.Value.IndexOf(ampTag);
if (ampPos >= 0)
{
context.Request.Path = new PathString(path.Value.Remove(ampPos, ampTag.Length));
context.Items.Add("amp", "true");
}
}
return _next(context);
}
}
public static class BuilderExtensions
{
public static IApplicationBuilder UseAmpMiddleware(this IApplicationBuilder app)
{
return app.UseMiddleware<AmpMiddleware>();
}
}
And call it in Startup:
app.UseAmpMiddleware();
Then can check in page and simple set another layout or limit some code, in his way no need to create separate page for amp version:
#if (HttpContext.Items.ContainsKey("amp"))
{
<b>Request AMP Version</b>
}