Aspnetcore: Debounce implementation with CancellationTokenSource (blazor server side .net core 3.0)

Created on 27 Oct 2019  路  3Comments  路  Source: dotnet/aspnetcore

Describe the bug

Debounce implementation (in blazor server side app .net core 3.0 with CancellationTokenSource) works well, but always writes errors in Debug Output:
Exception thrown: 'System.InvalidOperationException' in Microsoft.AspNetCore.Components.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll

Errors appear in Debug and Release modes

To Reproduce

Steps to reproduce the behavior:

  1. Create new Blazor server side app (.net core 3.0)
  2. Add following code to Index.razor:
@page "/"

<h1>Hello, world!</h1>

Welcome to your new app.

<div>
    Input text here: <MyChildComponent OnTyping="async e => await OnTypingAsync(e)" />
</div>
<div>
    Result: @result
</div>

@code {
    string result;

    public async Task OnTypingAsync(string myText)
    {
        await Task.Delay(1);//call GetDataAsync(myText) method

        result = myText;
        await InvokeAsync(StateHasChanged);
    }
}
  1. Add following code to MyChildComponent.razor:
@using System.Threading
@using System.Threading.Tasks

<input type="text" @oninput="async e => await OnInput(e)" />

@code {
    [Parameter] public EventCallback<string> OnTyping { get; set; }

    CancellationTokenSource Cts = new CancellationTokenSource();
    CancellationToken Ct;

    public async Task OnInput(ChangeEventArgs e)
    {
        Cts.Cancel();
        Cts = new CancellationTokenSource();
        Ct = Cts.Token;

        await Task.Delay(500, Ct).ContinueWith(async task =>
        {
            if (!task.IsCanceled)
            {
                await OnTyping.InvokeAsync(e.Value.ToString());
            }
        }, Ct);
    }
}
  1. Start typing text
  2. See errors:
    Exception thrown: 'System.InvalidOperationException' in Microsoft.AspNetCore.Components.dll
    Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll

Expected behavior

No errors

Screenshots

image

Additional context

stackoverflow discussions
github repo
BlazorFiddle

dotnet --info

C:\WINDOWS\system32>dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   3.0.100
 Commit:    04339c3a26

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18362
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\3.0.100\

Host (useful for support):
  Version: 3.0.0
  Commit:  7d57652f33

.NET Core SDKs installed:
  2.1.602 [C:\Program Files\dotnet\sdk]
  2.1.700 [C:\Program Files\dotnet\sdk]
  2.1.701 [C:\Program Files\dotnet\sdk]
  2.1.801 [C:\Program Files\dotnet\sdk]
  2.1.802 [C:\Program Files\dotnet\sdk]
  2.2.202 [C:\Program Files\dotnet\sdk]
  2.2.300 [C:\Program Files\dotnet\sdk]
  2.2.301 [C:\Program Files\dotnet\sdk]
  2.2.401 [C:\Program Files\dotnet\sdk]
  2.2.402 [C:\Program Files\dotnet\sdk]
  3.0.100 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Full Debug Output

'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Private.CoreLib.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'D:\blazor-debounce-bug-demonstration\DebounceSample\DebounceSample\bin\Debug\netcoreapp3.0\DebounceSample.dll'. Symbols loaded.
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Runtime.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Server.IIS.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Runtime.Extensions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Hosting.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Hosting.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Hosting.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.DependencyInjection.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.DependencyInjection.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Logging.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Collections.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\netstandard.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.ComponentModel.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.IO.FileSystem.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Hosting.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.EnvironmentVariables.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Primitives.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Threading.Tasks.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Linq.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Threading.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Server.Kestrel.Core.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Server.Kestrel.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Runtime.InteropServices.RuntimeInformation.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Server.IISIntegration.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.CommandLine.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.Core.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.FileProviders.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.FileProviders.Physical.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.FileExtensions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.Json.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.UserSecrets.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Configuration.Binder.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Private.Uri.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Runtime.InteropServices.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.IO.FileSystem.Watcher.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.ComponentModel.Primitives.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Collections.Concurrent.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.FileSystemGlobbing.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Threading.Timer.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Threading.Overlapped.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\Microsoft.Win32.Primitives.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Text.Json.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Memory.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Text.Encoding.Extensions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Buffers.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Numerics.Vectors.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Runtime.CompilerServices.Unsafe.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Options.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Logging.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Logging.EventLog.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Logging.Configuration.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Options.ConfigurationExtensions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Logging.Console.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Logging.Debug.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Logging.EventSource.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Diagnostics.Tracing.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Diagnostics.DiagnosticSource.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Http.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Http.Features.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Http.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Connections.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Net.Primitives.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Hosting.Server.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.HostFiltering.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.HttpOverrides.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Routing.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.ObjectPool.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Routing.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.ObjectModel.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Authentication.Core.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Authentication.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Security.Claims.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Components.Server.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'D:\blazor-debounce-bug-demonstration\DebounceSample\DebounceSample\bin\Debug\netcoreapp3.0\DebounceSample.Views.dll'. Symbols loaded.
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Razor.Runtime.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.Razor.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Authorization.Policy.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Authorization.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.DataAnnotations.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.RazorPages.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.ViewFeatures.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Linq.Expressions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Components.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.JSInterop.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.DataProtection.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.DataProtection.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Cryptography.Internal.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Antiforgery.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.WebEncoders.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Text.Encodings.Web.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Caching.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Caching.Memory.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Mvc.TagHelpers.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Razor.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.SignalR.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.SignalR.Core.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.SignalR.Common.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.StaticFiles.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Components.Authorization.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.WebSockets.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Http.Connections.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.SignalR.Protocols.Json.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Reflection.Emit.Lightweight.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.Localization.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Console.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Threading.Thread.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\System.Diagnostics.EventLog.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Collections.Specialized.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.ComponentModel.TypeConverter.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\Microsoft.Win32.Registry.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Xml.XDocument.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Private.Xml.Linq.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Private.Xml.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Resources.ResourceManager.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Diagnostics.Debug.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Security.Cryptography.Algorithms.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Text.RegularExpressions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Reflection.Emit.ILGeneration.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Reflection.Primitives.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Diagnostics.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.HttpsPolicy.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Http.Connections.Common.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Metadata.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\System.IO.Pipelines.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Security.Cryptography.Csp.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'Anonymously Hosted DynamicMethods Assembly'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Threading.Channels.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Net.Http.Headers.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Drawing.Primitives.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Html.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.FileProviders.Embedded.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.Extensions.FileProviders.Composite.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Xml.ReaderWriter.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Diagnostics.Abstractions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Threading.ThreadPool.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Security.Cryptography.X509Certificates.dll'. 
Microsoft.Hosting.Lifetime: Information: Application started. Press Ctrl+C to shut down.
Microsoft.Hosting.Lifetime: Information: Hosting environment: Development
Microsoft.Hosting.Lifetime: Information: Content root path: D:\blazor-debounce-bug-demonstration\DebounceSample\DebounceSample
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 GET https://localhost:44341/  
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 POST https://localhost:44341/_blazor/disconnect multipart/form-data; boundary=----WebKitFormBoundaryazBLm1q06LzpQbsz 359
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Security.Principal.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.ComponentModel.Annotations.dll'. 
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executing endpoint '/_Host'
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executing endpoint 'Blazor disconnect'
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.WebUtilities.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Security.Cryptography.Primitives.dll'. 
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executed endpoint 'Blazor disconnect'
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 129.3057ms 200 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Net.WebSockets.dll'. 
Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker: Information: Route matched with {page = "/_Host"}. Executing page /_Host
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\3.0.0\System.Security.Principal.Windows.dll'. 
Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker: Information: Executing an implicit handler method - ModelState is Valid
Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker: Information: Executed an implicit handler method, returned result Microsoft.AspNetCore.Mvc.RazorPages.PageResult.
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.DataProtection.Extensions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Http.Extensions.dll'. 
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App\3.0.0\Microsoft.AspNetCore.Components.Web.dll'. 
Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker: Information: Executed page /_Host in 186.5898ms
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 GET https://localhost:44341/css/site.css  
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 GET https://localhost:44341/_framework/blazor.server.js  
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 GET https://localhost:44341/css/bootstrap/bootstrap.min.css  
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executed endpoint '/_Host'
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 427.281ms 200 text/html; charset=utf-8
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware: Information: The file /css/site.css was not modified
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware: Information: The file /css/bootstrap/bootstrap.min.css was not modified
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware: Information: The file /_framework/blazor.server.js was not modified
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 67.893ms 304 application/javascript
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 67.893ms 304 text/css
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 164.86530000000002ms 304 text/css
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 GET https://localhost:44341/css/open-iconic/font/css/open-iconic-bootstrap.min.css  
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware: Information: The file /css/open-iconic/font/css/open-iconic-bootstrap.min.css was not modified
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 9.042300000000001ms 304 text/css
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 POST https://localhost:44341/_blazor/negotiate text/plain;charset=UTF-8 0
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executing endpoint '/_blazor/negotiate'
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executed endpoint '/_blazor/negotiate'
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 20.971400000000003ms 200 application/json
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/1.1 GET https://localhost:44341/_blazor?id=0iDT2Nlx1p_8aKlHXZQEAw  
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/2.0 GET https://localhost:44341/css/open-iconic/font/fonts/open-iconic.woff  
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executing endpoint '/_blazor'
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware: Information: The file /css/open-iconic/font/fonts/open-iconic.woff was not modified
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 21.9406ms 304 application/font-woff
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.Threading.Tasks.TaskCanceledException' in System.Private.CoreLib.dll
Exception thrown: 'System.InvalidOperationException' in Microsoft.AspNetCore.Components.dll
Exception thrown: 'System.InvalidOperationException' in Microsoft.AspNetCore.Components.dll
area-blazor question
Source
picture Marius-Kazlauskas

All 3 comments

@danroth27 Is this the thing that you wrote?

@Marius-Kazlauskas I'm not super familiar with the implementation, but a couple of things.

  • You need to always catch OperationCanceledException when using cancellation tokens.
  • You should avoid using continue with in your method as you are not capturing the SynchronizationContext and that's going to produce errors when you try to update the UI from the continuation callback.

If you do the two things above, the exceptions you are seeing should disappear.

I'm closing this issue for now as it's answered, feel free to comment if something is not clear and we can reopen it if necessary.

javiercn picture javiercn on 28 Oct 2019
👍1

Yeah, I did something similar in my BlazorWeather app: https://github.com/danroth27/BlazorWeather/blob/master/BlazorWeather.Core/Components/LocationSearch.razor. I also remember seeing exceptions like this and finding them annoying, but I believe @JamesNK said they were expected.

danroth27 picture danroth27 on 28 Oct 2019

@danroth27 one way to transparently go about this is to have an extension method on the IAsyncEnumerable you can call that essentially wraps the existing IAsyncEnumerable instance and captures the exceptions.

javiercn picture javiercn on 29 Oct 2019
👍1
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