[Solved] Blazor Server shows "There is no event handler associated with this event" after prolonged connection loss

[Sreejith]

We recently upgraded our application to .NET 10 and Telerik UI for Blazor 14.0.

Prior to the upgrade, whenever there was a network connectivity interruption in our Blazor Server application, users would typically see the standard yellow notification bar with a Reload button.

After the upgrade, we now see a "Rejoining the Server" popup instead. When a network disruption is introduced, the popup appears as expected. If connectivity is restored within a short period, the application reconnects successfully and users can continue working normally.

However, if the connection remains unavailable for approximately 5 minutes or longer, the "Rejoining the Server" popup disappears and the previously displayed page becomes visible again. At that point, the UI appears responsive, but when users attempt to interact with the application (for example, by clicking a menu item to navigate to another page), the following exception is thrown:

Uncaught (in promise) Error: System.ArgumentException: There is no event handler associated with this event. EventId: '1014'. (Parameter 'eventHandlerId')
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetRequiredEventBindingEntry(UInt64 eventHandlerId)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.DispatchEventAsync(UInt64 eventHandlerId, EventFieldInfo fieldInfo, EventArgs eventArgs, Boolean waitForQuiescence)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.DispatchEventAsync(UInt64 eventHandlerId, EventFieldInfo fieldInfo, EventArgs eventArgs)
   at InvokeStub_WebRendererInteropMethods.DispatchEventAsync(Object, Span`1)
   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
--- End of stack trace from previous location ---
   at Microsoft.JSInterop.Infrastructure.DotNetDispatcher.InvokeSynchronously(JSRuntime jsRuntime, DotNetInvocationInfo& callInfo, IDotNetObjectReference objectReference, String argsJson)
   at Microsoft.JSInterop.Infrastructure.DotNetDispatcher.BeginInvokeDotNet(JSRuntime jsRuntime, DotNetInvocationInfo invocationInfo, String argsJson)
    at w.endInvokeDotNetFromJS (https://localhost:5007/_framework/blazor.server.js:1:4494)
    at Xt._invokeClientMethod (https://localhost:5007/_framework/blazor.server.js:1:67169)
    at Xt._processIncomingData (https://localhost:5007/_framework/blazor.server.js:1:64534)
    at Xt.connection.onreceive (https://localhost:5007/_framework/blazor.server.js:1:58185)
    at i.onmessage (https://localhost:5007/_framework/blazor.server.js:1:82243)

Questions:

1. Is this a known issue with Telerik UI for Blazor 14.0 and/or .NET 10?

2. Is there a recommended configuration for handling long-running connection losses in Blazor Server applications?

3. What is the recommended approach for handling this scenario? After the reconnection attempt times out, should the application force a full page reload, or is there a preferred way to recover from the stale/non-functional event handlers and restore a valid Blazor circuit?

Environment:

• .NET 10
• Telerik UI for Blazor 14.0
• Blazor Server

[Dimo]

Hello Sreejith,

The error is Blazor-specific and I believe that the Telerik components themselves are have no control over it. There has been multiple issues about such an error in the dotnet repo in the past year with the most recent (and .NET 10 related) probably being: https://github.com/dotnet/aspnetcore/issues/64607 (although I am not sure if it's the same situation)

With regard to configuration and SignalR connection monitoring, I recommend ASP.NET Core Blazor SignalR guidance.

For the sake of research, you can keep .NET 10 in the app and only switch the Telerik UI for Blazor version (the valid options are versions from 12 to latest) to see if the components are causing the problem.

Regards,
Dimo
Progress Telerik