如何检查 controller 和/或操作是否作为来自中间件的有效端点存在？

Question

I need to figure out from a middleware if a route or context points to a valid endpoint in my API. I want to do this in order to send a valid json-formatted error response, instead of the default empty error message that the API sends.

An alternative solution that figures out that the endpoint resulted in nothing is fine too. My first thought was to use a middleware, but perhaps sending an error with a fall-back controller works too?

Answer 1

I would like to give an answer to my own question, as I have found a way to manually check if a route exists. This was something I did not think of at the time, as I did not realise you could get information about your API through a dependency.

The way I have done this now is to make use of the IActionDescriptorCollectionProvider provider. This will allow me to receive all current routes in the API. Using this, I created the following middleware:

public async Task InvokeAsync(HttpContext context)
{
    var path = context.Request.Path.Value;
    var routes = _actionDescriptorCollectionProvider.ActionDescriptors.Items.Select(ad => $"/{ad.AttributeRouteInfo.Template}").ToList();

    if (!routes.Any(route => path.Equals(route, StringComparison.InvariantCultureIgnoreCase))) {
        context = await context.HandleRequest(HttpStatusCode.NotFound, "RouteNotFound", "De server heeft geen geldige actie voor de gegeven route.");
        return;
    }

    await _next(context);
}

This fully allows me to respond with a custom error (this is using HandleRequest(), which is an extension of my own), and handle the rest in the frontend.

I found another way to solve this to use pre-initialised documentation by the API. I'm not sure what to call it, but adding the following code to your csproj file creates an XML which gives the same benefits:

<NoWarn>$(NoWarn);1591</NoWarn>
<DocumentationFile>Files\Documentation\$(Configuration)_$(AssemblyName)_doc.xml</DocumentationFile>

This means that the XML has be parsed of course.

I am still looking for different solutions, perhaps better ones if there are problems with this one.