Why this throws an exception? was this changed?

[iam3yal]

I have a custom grid component and my row and cell components have few parameters that are an implementation details so consumers shouldn't have access to them, I doubt the following approach below changed because based on this post it should work and I tested my grid both in .NET 6 and 7 just a month ago, it worked only now I'm getting an exception:

So I made a new Blazor Server App (Empty) project with a simple component with a similar code that worked for my grid before like this:

@code {
    private object? Item { get; set; }
    
    public override Task SetParametersAsync(ParameterView parameters)
    {
        Item = parameters.GetValueOrDefault<object>("Item");

        return base.SetParametersAsync(parameters);
    }
}

<C Item="foo"></C>

Only now I'm getting the following exception:

InvalidOperationException: Object of type 'BlazorTest.Pages.C' has a property matching the name 'Item', but it does not have [ParameterAttribute] or [CascadingParameterAttribute] applied.

I've used .NET 7.0.307 for this example.

Here is the Stack Trace:

ystem.InvalidOperationException: Object of type 'BlazorTest.Pages.C' has a property matching the name 'Item', but it does not have [ParameterAttribute] or [CascadingParameterAttribute] applied.
   at Microsoft.AspNetCore.Components.Reflection.ComponentProperties.ThrowForUnknownIncomingParameterName(Type targetType, String parameterName)
   at Microsoft.AspNetCore.Components.Reflection.ComponentProperties.SetProperties(ParameterView& parameters, Object target)
   at Microsoft.AspNetCore.Components.ParameterView.SetParameterProperties(Object target)
   at Microsoft.AspNetCore.Components.ComponentBase.SetParametersAsync(ParameterView parameters)
   at BlazorTest.Pages.C.SetParametersAsync(ParameterView parameters) in /Users/eyal/Development/Projects/BlazorTest/BlazorTest/Pages/C.razor:line 8
   at Microsoft.AspNetCore.Components.Rendering.ComponentState.SupplyCombinedParameters(ParameterView directAndCascadingParameters)
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.HandleExceptionViaErrorBoundary(Exception error, ComponentState errorSourceOrNull)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToPendingTasks(Task task, ComponentState owningComponentState)
   at Microsoft.AspNetCore.Components.Rendering.ComponentState.SupplyCombinedParameters(ParameterView directAndCascadingParameters)
   at Microsoft.AspNetCore.Components.Rendering.ComponentState.SetDirectParameters(ParameterView parameters)
   at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InitializeNewComponentFrame(DiffContext& diffContext, Int32 frameIndex)
   at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InitializeNewSubtree(DiffContext& diffContext, Int32 frameIndex)
   at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InsertNewFrame(DiffContext& diffContext, Int32 newFrameIndex)
   at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange(DiffContext& diffContext, Int32 oldStartIndex, Int32 oldEndIndexExcl, Int32 newStartIndex, Int32 newEndIndexExcl)
   at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.ComputeDiff(Renderer renderer, RenderBatchBuilder batchBuilder, Int32 componentId, ArrayRange`1 oldTree, ArrayRange`1 newTree)
   at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, Exception& renderFragmentException)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessPendingRender()
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToRenderQueue(Int32 componentId, RenderFragment renderFragment)
   at Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged()
   at Microsoft.AspNetCore.Components.ComponentBase.CallOnParametersSetAsync()
   at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()
   at Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.HandleExceptionViaErrorBoundary(Exception error, ComponentState errorSourceOrNull)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToPendingTasks(Task task, ComponentState owningComponentState)
   at Microsoft.AspNetCore.Components.Rendering.ComponentState.SupplyCombinedParameters(ParameterView directAndCascadingParameters)
   at Microsoft.AspNetCore.Components.Rendering.ComponentState.SetDirectParameters(ParameterView parameters)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.RenderRootComponentAsync(Int32 componentId, ParameterView initialParameters)
   at Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.CreateInitialRenderAsync(Type componentType, ParameterView initialParameters)
   at Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.RenderComponentAsync(Type componentType, ParameterView initialParameters)
   at Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext.<>c__11`1.<<InvokeAsync>b__11_0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.ViewFeatures.StaticComponentRenderer.PrerenderComponentAsync(ParameterView parameters, HttpContext httpContext, Type componentType)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ComponentRenderer.PrerenderedServerComponentAsync(HttpContext context, ServerComponentInvocationSequence invocationId, Type type, ParameterView parametersCollection)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ComponentRenderer.RenderComponentAsync(ViewContext viewContext, Type componentType, RenderMode renderMode, Object parameters)
   at Microsoft.AspNetCore.Mvc.TagHelpers.ComponentTagHelper.ProcessAsync(TagHelperContext context, TagHelperOutput output)
   at Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner.<RunAsync>g__Awaited|0_0(Task task, TagHelperExecutionContext executionContext, Int32 i, Int32 count)
   at BlazorTest.Pages.Pages__Host.<ExecuteAsync>b__14_1() in /Users/eyal/Development/Projects/BlazorTest/BlazorTest/Pages/_Host.cshtml:line 15
   at Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext.SetOutputContentAsync()
   at BlazorTest.Pages.Pages__Host.ExecuteAsync()
   at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)
   at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, Boolean invokeViewStarts)
   at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable`1 statusCode)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable`1 statusCode)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

[Dreamescaper]

I don't think that was ever a supported scenario. But you probably can do smth like this:

  public override Task SetParametersAsync(ParameterView parameters)
  {
      Item = parameters.GetValueOrDefault<object>("Item");
      return base.SetParametersAsync(ParameterView.Empty);
  }

[iam3yal]

@Dreamescaper But I'm pretty sure it worked for me before, this is the strange thing and I don't think I've passed ParameterView.Empty but I could be wrong. :)

[iam3yal]

@Dreamescaper Okay I tried it and you're right the moment you pass ParameterView.Empty it works although I'm pretty sure I didn't need to do it before so I think something is odd, however, the issue with the solution you provided is that now I have to assign all the properties manually, attempting to call SetParameterProperties will throw the same exception.

[Dreamescaper]

Let me clarify. Maybe it worked before (I haven't checked), it's just that I don't think it was ever the supported scenario that was guarenteed to work. It certainly did fail if there was no such property at all, so it makes sense that behavior matches.

As an alternative, you can do smth like that

  private object? Item => UnmatchedValues.TryGetValue("Item", out var item) ? item : null;

  [Parameter(CaptureUnmatchedValues = true)]
  public Dictionary<string, object> UnmatchedValues { get; set; }

[iam3yal]

@Dreamescaper Well, I ended up having a parameter called UserData up in the hierarchy where I can pass any arbitrary object to it similar to the Tag property we have in WinForms and WPF. :)