dotnet/aspnetcore · error · InvalidOperationException

Unable to find the provided template '{template}'

Error message

Unable to find the provided template '{template}'

What it means

RouteTableFactory.GetEntry looks up a previously-parsed route template by its raw text among the templates derived from assembly scanning. If the requested template string does not case-insensitively equal any parsed template's RawText, the lookup fails and the factory throws InvalidOperationException. This indicates the caller asked for a template that was never registered as a [Route] on a component.

Source

Thrown at src/Components/Components/src/Routing/RouteTableFactory.cs:190

        var templates = GetTemplates(pageType);
        var result = ComputeTemplateGroupInfo(templates);

        RoutePattern? parsedTemplate = null;
        HashSet<string>? routeParameterNames = null;
        for (var i = 0; i < result.ParsedTemplates.Length; i++)
        {
            var (parsed, parameters) = result.ParsedTemplates[i];
            if (string.Equals(parsed.RawText, template, StringComparison.OrdinalIgnoreCase))
            {
                parsedTemplate = parsed;
                routeParameterNames = parameters;
                break;
            }
        }

        if (parsedTemplate == null)
        {
            throw new InvalidOperationException($"Unable to find the provided template '{template}'");
        }

        return new InboundRouteEntry()
        {
            Handler = pageType,
            RoutePattern = parsedTemplate,
            UnusedRouteParameterNames = GetUnusedParameterNames(result.AllRouteParameterNames, routeParameterNames!),
        };
    }
    private static void DetectAmbiguousRoutes(TreeRouteBuilder builder)
    {
        var seen = new HashSet<InboundRouteEntry>(new InboundRouteEntryAmbiguityEqualityComparer());
        seen.EnsureCapacity(builder.InboundEntries.Count);

        for (var i = 0; i < builder.InboundEntries.Count; i++)
        {
            var current = builder.InboundEntries[i];

View on GitHub (pinned to 3600ca084e)

Solutions

1. Confirm the template string exactly matches a [Route(...)] attribute in one of the assemblies supplied to RouteTableFactory (case-insensitive, including leading/trailing slashes).
2. Ensure the assembly containing the route is included in the AppAssembly / AdditionalAssemblies passed to the Router.
3. Search the codebase for [Route("<template>")] to confirm the attribute exists and is spelled identically.
4. If the route is dynamic, register a matching template attribute on a component before requesting it.

Example fix

// before — typo in requested template
var entry = factory.GetEntry("usrs/{id}", pageType); // no [Route("usrs/{id}")] exists
// after
var entry = factory.GetEntry("users/{id}", pageType); // matches [Route("users/{id}")]

// Confirm a template is registered before requesting it from RouteTableFactory.
bool IsRegistered(IEnumerable<string> templates, string requested)
    => templates.Any(t => string.Equals(t, requested, StringComparison.OrdinalIgnoreCase));

When it happens

Trigger: Calling the internal RouteTableFactory with a template string that does not match any [Route("...")] attribute present in the supplied assemblies. Common from hot-reload invalidation, programmatic route generation, or unit tests that pass arbitrary template strings.

Common situations: Adding a [Route] attribute with a typo and referencing the corrected string elsewhere; referencing a route that lives in an assembly not passed to the factory; renaming a route template in code but keeping the old string in a lookup table; multi-assembly apps where the route was contributed by an optional plugin that is not loaded.

Related errors

• The following routes are ambiguous: '{existingText}' in '{ex
• The {nameof(RouteView)} component requires a non-null value
• The {nameof(Router)} component requires a value for the para
• The {nameof(Router)} component requires a value for the para
• Setting {nameof(NotFound)} and {nameof(NotFoundPage)} proper

AI-assisted analysis of dotnet/aspnetcore@3600ca084e (2026-08-11). Data as JSON: /api/errors/fbec70d524fb3bb3. Report an issue: GitHub.