How to work around "A catch-all parameter can only appear as the last segment of the route template." - asp.net-core

Question

If I have a controller with an action method that uses attribute based routing and declare it like this, all is well:
[HttpGet]
[Route("/dev/info/{*somevalue}")]
public IActionResult Get(string somevalue) {
return View();
}
I can route to the above action method for example by specifying a url that ends in /dev/info/hello-world or /dev/info/new-world
However my business requirement is to have a urls that look like this: /dev/hello-world/info or /dev/new-world/info And there is an endless set of such urls that all need to route to the same action method on the controller.
I thought to set up the attribute based route on the action method as follows:
[HttpGet]
[Route("/dev/{*somevalue}/info/")]
public IActionResult Get(string somevalue) {
return View();
}
But when I do that I get the following error as soon as the web project runs:
An unhandled exception occurred while processing the request.
RouteCreationException: The following errors occurred with attribute routing information:
For action: 'App.SomeController.Get (1-wwwSomeProject)'
Error: A catch-all parameter can only appear as the last segment of the route template.
Parameter name: routeTemplate
Microsoft.AspNetCore.Mvc.Internal.AttributeRoute.GetRouteInfos(IReadOnlyList actions)
There has to be some way to work around this error. Know a way?

Answer 1

Middleware is the way to achieve this.
If you need an api response is easy to implement inline.
if (app.Environment.IsDevelopment())
{
app.Use(async (context, next) =>
{
Console.WriteLine(context.Request.Path);
if (context.Request.Path.ToString().EndsWith("/info"))
{
// some logic
await context.Response.WriteAsync("Terminal Middleware.");
return;
}
await next(context);
});
}
If you need to call a controller you can simply edit request path via middleware to achieve your requirement.
You can find an example here: https://stackoverflow.com/a/50010787/3120219

Answer 2

It is possible to achieve this by using the regular expression:
[HttpGet]
[Route(#"/dev/{somevalue:regex(^.*$)}/info/")]
public IActionResult Get(string somevalue)
{
return View();
}
About routing constrain using the regular expressions see in the documentation: Route constraint reference
The regular expression tokens explanation:
Token
Explanation
^
Asserts position at start of a line
.
Matches any character (except for line terminators)
*
Matches the previous token between zero and unlimited times, as many times as possible
$
Asserts position at the end of a line
If it's required to have the “world”suffix in the second segment then add this suffix to the pattern like the following: [Route(#"/dev/{somevalue:regex(^.*world$)}/info/")].