dotnet/aspnetcore · error · InvalidOperationException

The component type ' ' has a fixed rendermode of ' ', so it…

Error message

The component type '{componentType}' has a fixed rendermode of '{componentTypeRenderMode}', so it is not valid to specify any rendermode when using this component.

What it means

When a component type has a fixed render mode (via a RenderMode attribute such as [RenderModeInteractiveServer]) and the call site also specifies a render mode, the two conflict. Only one source of render mode is permitted, so ComponentFactory throws InvalidOperationException.

Solutions

  1. Remove the render mode from the call site since the component already declares a fixed one.
  2. Alternatively, remove the RenderMode attribute from the component if call-site flexibility is desired.
  3. Document which components have fixed render modes so callers do not override them.

Example fix

// before
// MyComponent.razor.cs: [RenderModeInteractiveServer]
<MyComponent RenderMode="InteractiveServer" />
// after
<MyComponent />
Defensive patterns

Strategy: validation

Validate before calling

// Ensure a component is not decorated with a fixed RenderMode attribute when callers also pass a render mode.
var hasFixed = componentType.GetCustomAttributes(true).Any(a => a is IComponentRenderMode);
if (hasFixed) { /* do not pass RenderMode at call site */ }

Prevention

When it happens

Trigger: <MyComponent RenderMode="InteractiveServer" /> where MyComponent is decorated with [RenderModeInteractiveServer] (or any fixed RenderMode attribute).

Common situations: Adding a RenderMode attribute to a component and forgetting to drop the call-site RenderMode argument, or upgrading to .NET 8+ interactive rendering and specifying the mode in both places.

Related errors

AI-assisted analysis of dotnet/aspnetcore@3600ca084e (2026-08-11). Data as JSON: /api/errors/514796de0b3d7cd3. Report an issue: GitHub.

Appendix: source

Thrown at src/Components/Components/src/ComponentFactory.cs:74

    public IComponent InstantiateComponent(IServiceProvider serviceProvider, [DynamicallyAccessedMembers(Component)] Type componentType, IComponentRenderMode? callerSpecifiedRenderMode, int? parentComponentId)
    {
        var componentTypeRenderMode = GetComponentTypeRenderMode(componentType);
        IComponent component;

        if (componentTypeRenderMode is null && callerSpecifiedRenderMode is null)
        {
            // Typical case where no rendermode is specified in either location. We don't call ResolveComponentForRenderMode in this case.
            component = _componentActivator.CreateInstance(componentType);
        }
        else
        {
            // At least one rendermode is specified. We require that it's exactly one, and use ResolveComponentForRenderMode with it.
            var effectiveRenderMode = callerSpecifiedRenderMode is null
                ? componentTypeRenderMode!
                : componentTypeRenderMode is null
                    ? callerSpecifiedRenderMode
                    : throw new InvalidOperationException($"The component type '{componentType}' has a fixed rendermode of '{componentTypeRenderMode}', so it is not valid to specify any rendermode when using this component.");
            component = _renderer.ResolveComponentForRenderMode(componentType, parentComponentId, _componentActivator, effectiveRenderMode);
        }

        if (component is null)
        {
            // The default activator/resolver will never do this, but an externally-supplied one might
            throw new InvalidOperationException($"The component activator returned a null value for a component of type {componentType.FullName}.");
        }

        if (!_propertyInjectionDisabled)
        {
            PerformPropertyInjection(serviceProvider, component);
        }

        return component;
    }

    private void PerformPropertyInjection(IServiceProvider serviceProvider, IComponent instance)

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