Include a file extension in ASP.NET Core MVC routes

user_269629 0
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I'm porting a legacy application to ASP.NET Core and I'm trying to keep the URLs consistent. Ideally I need to include a "file extension" in the URL, e.g. /Home/Index.ext should route to the Index action on HomeController.

I've started with the standard web application template in Visual Studio and tried modifying the default route:

endpoints.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}.ext/{id?}");

A request for /Home/Index.ext then gives the error:

An unhandled exception occurred while processing the request.
AmbiguousMatchException: The request matched multiple endpoints. Matches:

WebApplication1.Controllers.HomeController.Index (WebApplication1)
WebApplication1.Controllers.HomeController.Privacy (WebApplication1)
WebApplication1.Controllers.HomeController.Error (WebApplication1)
Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.ReportAmbiguity(CandidateState[] candidateState)

I can't see why it's not taking the action name from this URL to select the correct action. Is there some way I can change this route pattern to get it to match this correctly?

asp.net-core asp.net-mvc
3 Answers

You can do this with the IOutboundParameterTransformer that's inside Microsoft.AspNetCore.Routing.

Simply create a transformer as follows (if you want the .ext extension):

public class AddExtensionTransformer : IOutboundParameterTransformer
{
    public string TransformOutbound(object value)
        => value + ".ext";
}

Then you register it as a constraint (I used the name addextension):

services.Configure<RouteOptions>(options =>
{
    options.ConstraintMap["addextension"] = typeof(AddExtensionTransformer);
});

And then in your route, you simply use addextension as a route constraint (using the : delimiter).

For the default route from your post, it will look like this:

endpoints.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action:addextension=Index}/{id?}");

ASP.NET Core will now also automatically generate URLs like /Home/Index.ext whenever you tell it to generate an action URL.

So it not only parses them but also generates them (works both ways).

user_1083740

You can then use an Attribute Route like this:-

[Route("Home/Index.ext")]
public ActionResult Index() {... }

For more information read this Documentation

user_114632960

You can use URL Rewriting Middleware like below(html extension as a sample):

1.Custom a class containing ReWriteRequests

public class RewriteRules
{  
    public static void ReWriteRequests(RewriteContext context)
    {
        var request = context.HttpContext.Request;

        if (request.Path.Value.EndsWith(".html", StringComparison.OrdinalIgnoreCase))
        {
            context.HttpContext.Request.Path = context.HttpContext.Request.Path.Value.Replace(".html", "");

        }
    }
}

2.Startup.cs:

Be sure use URL Rewriting Middleware before app.UseStaticFiles();

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseRewriter(new RewriteOptions()
                    .Add(RewriteRules.ReWriteRequests)
                    );

    app.UseHttpsRedirection();
    app.UseStaticFiles();

    app.UseRouting();

    app.UseAuthentication();
    app.UseAuthorization();
        
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute(
            name: "default",
            pattern: "{controller=Home}/{action=Index}/{id?}");
        endpoints.MapRazorPages();
    });
}

Reference:

URL Rewriting Middleware in ASP.NET Core

user_113988100
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