dotnet/aspnetcore · error · InvalidOperationException

No component found for route

Error message

No component found for route '{route}'. Ensure the route matches a component with a [Route] attribute.

What it means

RenderComponentByRoute resolves the requested route to a component type via FindComponentTypeByRoute; if no component in the configured assemblies declares a matching [Route], the type lookup returns null and the method throws InvalidOperationException with a hint to verify the [Route] attribute. This is the explicit failure mode for the programmatic render-by-route API (used by tests and Server/renderer entry points).

Solutions

Confirm the route string exactly matches a [Route("...")] on a component, including leading slash and parameter placeholders.
Add the assembly containing the page to AppAssembly / AdditionalAssemblies on the Router.
If publishing with trimming, ensure the page type and its [Route] attribute are root-preserved (e.g. via DynamicallyAccessedMembers or a linker XML).
Verify the page component compiles and its generated route attribute is present (check with reflection in a test).

Example fix

// before
renderer.RenderComponentByRoute("/usrs/42");  // typo
// after
renderer.RenderComponentByRoute("/users/42"); // matches [Route("/users/{id}")]

Defensive patterns

Strategy: validation

Validate before calling

// Validate the route is known before invoking RenderComponentByRoute.
if (!knownRoutes.Contains(route, StringComparer.OrdinalIgnoreCase))
    throw new InvalidOperationException($"No registered route matches '{route}'.");

Try / catch

// Only meaningful in test harnesses; otherwise the route should already be validated.
try { renderer.RenderComponentByRoute(route); }
catch (InvalidOperationException ex) when (ex.Message.Contains("No component found for route"))
{
    // log and fall back to a known route
}

Prevention

Keep a list of valid routes (derived from [Route] attributes) and validate before programmatic render.
Include every page-bearing assembly in the Router configuration.
When publishing trimmed, root-preserve page types and their [Route] attributes.
Add a test enumerating routes and rendering each.

When it happens

Trigger: Calling RenderComponentByRoute (or an internal caller such as the test harness / pre-rendering pipeline) with a route string that matches no [Route] attribute in the scanned assemblies. Also triggered by navigation to a path before the page component has been registered (race with route table population).

Common situations: Programmatically rendering a component by URL in a test and mistyping the route; the target page is in an assembly not passed to the Router; the [Route] uses a parameter placeholder that does not match the supplied literal route; trimming removed the page or its [Route] attribute at publish time.

Related errors

AI-assisted analysis of dotnet/aspnetcore@3600ca084e (2026-08-11). Data as JSON: /api/errors/0d52cd1eefbf30a9. Report an issue: GitHub.

Appendix: source

Thrown at src/Components/Components/src/Routing/Router.cs:416

                _renderHandle.Render(builder => RenderComponentByRoute(builder, args.Path));
            }
            else
            {
                // Having the path set signals to the endpoint renderer that router handled rendering.
                args.Path = _notFoundPageRoute;
                RenderNotFound();
            }
            Log.DisplayingNotFound(_logger, args.Path);
        }
    }

    internal void RenderComponentByRoute(RenderTreeBuilder builder, string route)
    {
        var componentType = FindComponentTypeByRoute(route);

        if (componentType is null)
        {
            throw new InvalidOperationException($"No component found for route '{route}'. " +
                $"Ensure the route matches a component with a [Route] attribute.");
        }

        builder.OpenComponent<RouteView>(0);
        builder.AddAttribute(1, nameof(RouteView.RouteData),
            new RouteData(componentType, new Dictionary<string, object>()));
        builder.CloseComponent();
    }

    [return: DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]
    internal Type? FindComponentTypeByRoute(string route)
    {
        RefreshRouteTable();
        var normalizedRoute = route.StartsWith('/') ? route : $"/{route}";

        var context = new RouteContext(normalizedRoute);
        Routes.Route(context);

View on GitHub (pinned to 3600ca084e)