Replacement for WebAssemblyHttpMessageHandler?

[jernejk]

Describe the bug

In the latest release, .NET Core 3.1 Preview 3, WebAssemblyHttpMessageHandler was removed with no obvious replacement I could find for client-side Blazor.

I'm back to having "Call failed. Operation is not supported on this platform." exception when using Flurl. What is the correct HttpClientFactory for client-side Blazor?

To Reproduce

In Startup, ConfigureServices:

FlurlHttp.Configure(settings =>
{
    settings.HttpClientFactory = new DefaultHttpClientFactory();
});

Execute:

var response = await new Url(url).GetAsync();

var content = await response.Content.ReadAsStringAsync();

Direct usage of HttpClient works.

Previous workaround:

    public class HttpClientFactoryForBlazor : DefaultHttpClientFactory
    {
        public override HttpMessageHandler CreateMessageHandler()
        {
            return new WebAssemblyHttpMessageHandler();
        }
    }

// In Startup, ConfigureServices:
FlurlHttp.Configure(settings =>
{
    settings.HttpClientFactory = new HttpClientFactoryForBlazor();
});

I would still like to use Flurl because I have unit tests that verify that requests were generated correctly. I'm building a Cognitive Services API explorer, which can generate cURL as well as make a request to Cognitive Services.

For now, I'll revert back to Preview 2.

Further technical details

• ASP.NET Core 3.1.0-preview3.19555.2
• Include the output of dotnet --info

.NET Core SDK (reflecting any global.json):
 Version:   3.1.100-preview3-014645
 Commit:    b32d27f4b3

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18362
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\3.1.100-preview3-014645\

Host (useful for support):
  Version: 3.1.0-preview3.19553.2
  Commit:  13f35c3d86

.NET Core SDKs installed:
  2.1.201 [C:\Program Files\dotnet\sdk]
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.400 [C:\Program Files\dotnet\sdk]
  2.1.401 [C:\Program Files\dotnet\sdk]
  2.1.402 [C:\Program Files\dotnet\sdk]
  2.1.403 [C:\Program Files\dotnet\sdk]
  2.1.500 [C:\Program Files\dotnet\sdk]
  2.1.502 [C:\Program Files\dotnet\sdk]
  2.1.503 [C:\Program Files\dotnet\sdk]
  2.1.504 [C:\Program Files\dotnet\sdk]
  2.1.505 [C:\Program Files\dotnet\sdk]
  2.1.507 [C:\Program Files\dotnet\sdk]
  2.1.508 [C:\Program Files\dotnet\sdk]
  2.1.600 [C:\Program Files\dotnet\sdk]
  2.1.601 [C:\Program Files\dotnet\sdk]
  2.1.602 [C:\Program Files\dotnet\sdk]
  2.1.604 [C:\Program Files\dotnet\sdk]
  2.1.700-preview-009597 [C:\Program Files\dotnet\sdk]
  2.1.700-preview-009601 [C:\Program Files\dotnet\sdk]
  2.1.700-preview-009618 [C:\Program Files\dotnet\sdk]
  2.1.700 [C:\Program Files\dotnet\sdk]
  2.1.701 [C:\Program Files\dotnet\sdk]
  2.1.800-preview-009677 [C:\Program Files\dotnet\sdk]
  2.1.800-preview-009696 [C:\Program Files\dotnet\sdk]
  2.1.800 [C:\Program Files\dotnet\sdk]
  2.1.801 [C:\Program Files\dotnet\sdk]
  2.2.100 [C:\Program Files\dotnet\sdk]
  2.2.204 [C:\Program Files\dotnet\sdk]
  2.2.300 [C:\Program Files\dotnet\sdk]
  2.2.301 [C:\Program Files\dotnet\sdk]
  2.2.400-preview-010195 [C:\Program Files\dotnet\sdk]
  2.2.400-preview-010219 [C:\Program Files\dotnet\sdk]
  2.2.400 [C:\Program Files\dotnet\sdk]
  2.2.401 [C:\Program Files\dotnet\sdk]
  3.0.100-preview7-012821 [C:\Program Files\dotnet\sdk]
  3.0.100-preview8-013656 [C:\Program Files\dotnet\sdk]
  3.0.100 [C:\Program Files\dotnet\sdk]
  3.1.100-preview1-014459 [C:\Program Files\dotnet\sdk]
  3.1.100-preview2-014569 [C:\Program Files\dotnet\sdk]
  3.1.100-preview3-014645 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  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 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.4 [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 2.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  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 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.4 [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-preview8.19405.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]

  Microsoft.AspNetCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.0-preview3.19555.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]

  Microsoft.NETCore.App 2.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.3-servicing-26724-03 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.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 2.2.0 [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-preview8-28405-07 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.0-preview3.19553.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.0-preview8-28405-07 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.0-preview3.19553.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download 

• Visual Studio 2019 16.4 Preview 5

[javiercn]

@jernejk thanks for contacting us.

@SteveSandersonMS Can you provide guidance here? I thought that as part of moving to netstandard2.1 we were using the out of the box httpclient.

[IvanJosipovic]

I'm also encountering an issue with 3.1 Preview 3.

I'm using the Kubernetes C# Client in Blazor:

In Preview 2 the following worked:

services.AddTransient<WebAssemblyHttpMessageHandler>();

// Setup the http client
services.AddHttpClient("K8s")
   .ConfigurePrimaryHttpMessageHandler<WebAssemblyHttpMessageHandler>()
   .AddTypedClient<IKubernetes>((httpClient, serviceProvider) => new Kubernetes(serviceProvider.GetRequiredService<KubernetesClientConfiguration>(), httpClient));

In Preview 3, I changed the code to:

// Setup the http client
services.AddHttpClient("K8s")
   .AddTypedClient<IKubernetes>((httpClient, serviceProvider) => new Kubernetes(serviceProvider.GetRequiredService<KubernetesClientConfiguration>(), httpClient));

Now, the app throws the following exception:
Please note: Linker is disabled!

Unhandled exception rendering component:
System.NotImplementedException: Cannot invoke method because it was wiped. See stack trace for details.
  at System.Net.Http.HttpClientHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) <0x387f300 + 0x00004> in <dff681a802cd429faf7e3556cf8262da>:0 
  at System.Net.Http.DelegatingHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) <0x386ad60 + 0x00036> in <dff681a802cd429faf7e3556cf8262da>:0 
  at Microsoft.Extensions.Http.Logging.LoggingHttpMessageHandler.<>n__0 (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) <0x387f1a8 + 0x0000e> in <f0b7b3feb5344f5fb506a82d63ee937f>:0 
  at Microsoft.Extensions.Http.Logging.LoggingHttpMessageHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) <0x387e7c0 + 0x0006e> in <f0b7b3feb5344f5fb506a82d63ee937f>:0 
  at Microsoft.Extensions.Http.Logging.LoggingScopeHttpMessageHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) <0x386bd10 + 0x00148> in <f0b7b3feb5344f5fb506a82d63ee937f>:0 
  at System.Net.Http.HttpClient.FinishSendAsyncBuffered (System.Threading.Tasks.Task`1[TResult] sendTask, System.Net.Http.HttpRequestMessage request, System.Threading.CancellationTokenSource cts, System.Boolean disposeCts) <0x3891600 + 0x00264> in <dff681a802cd429faf7e3556cf8262da>:0 
  at k8s.Kubernetes.ListNamespaceWithHttpMessagesAsync (System.Nullable`1[T] allowWatchBookmarks, System.String continueParameter, System.String fieldSelector, System.String labelSelector, System.Nullable`1[T] limit, System.String resourceVersion, System.Nullable`1[T] timeoutSeconds, System.Nullable`1[T] watch, System.String pretty, System.Collections.Generic.Dictionary`2[TKey,TValue] customHeaders, System.Threading.CancellationToken cancellationToken) <0x38471a0 + 0x0079a> in <d1571f80f038409685da34e57cdd6943>:0 
  at k8s.KubernetesExtensions.ListNamespaceAsync (k8s.IKubernetes operations, System.Nullable`1[T] allowWatchBookmarks, System.String continueParameter, System.String fieldSelector, System.String labelSelector, System.Nullable`1[T] limit, System.String resourceVersion, System.Nullable`1[T] timeoutSeconds, System.Nullable`1[T] watch, System.String pretty, System.Threading.CancellationToken cancellationToken) <0x381d5f8 + 0x0012e> in <d1571f80f038409685da34e57cdd6943>:0 
  at UI.Components.Namespaces.OnInitializedAsync () [0x00058] in C:\Repos\UI\src\UI\Components\Namespaces.razor.cs:25 
  at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync () <0x3523428 + 0x0013e> in <44d78cab266c4647aa96aadd4455da2c>:0 

[campersau]

I also encountered this issue and found a very hacky workaround based on code from here https://github.com/aspnet/AspNetCore/blob/271ebe019823e8e6a751429cd350c2db76ebab05/src/Components/Blazor/Blazor/src/Http/WebAssemblyHttpMessageHandlerOptions.cs:

var wasmHttpMessageHandlerType = Assembly.Load("WebAssembly.Net.Http").GetType("WebAssembly.Net.Http.HttpClient.WasmHttpMessageHandler");
var wasmHttpMessageHandler = (HttpMessageHandler)Activator.CreateInstance(wasmHttpMessageHandlerType);
var httpClient = new HttpClient(wasmHttpMessageHandler);

[IvanJosipovic]

@campersau, your solution worked!

I've implemented the following:

// Setup the http client
services.AddHttpClient("K8s")
    .ConfigurePrimaryHttpMessageHandler( x=> 
    {
        var wasmHttpMessageHandlerType = Assembly.Load("WebAssembly.Net.Http").GetType("WebAssembly.Net.Http.HttpClient.WasmHttpMessageHandler");
        return (HttpMessageHandler)Activator.CreateInstance(wasmHttpMessageHandlerType);
    })
    .AddTypedClient<IKubernetes>((httpClient, serviceProvider) => new Kubernetes(serviceProvider.GetRequiredService<KubernetesClientConfiguration>(), httpClient));

[szmalec]

An explanation of the reason for removing the WebAssemblyHttpMessageHandler class may probably be here: #16631 (comment)
Is this correct?

[campersau]

The mono wasm HttpClientHandler does not support a lot of things and throws PlatformNotSupportedExceptions when setting some properties.
This might be the real issue for the OP here because Flurls DefaultHttpClientFactory always sets AutomaticDecompression without checking if SupportsAutomaticDecompression is true.

For the rest of us it looks like dotnet/blazor#1938 might fix our issues.

[SteveSandersonMS]

Yes, this is fixed with dotnet/blazor#1938, which will be included in the next release in December.

If you find there are parts of the API surface that don't work, but you believe they should work from a browser context (that is, it's not just a JavaScript limitation), then could you please report the details of that as a separate issue? Thanks!

[jernejk]

Awesome!
Is this coming with Preview 4?

PS: Workaround from @campersau is working for me, which is to create an instance from WebAssembly.Net.Http assembly.

public class HttpClientFactoryForBlazor : DefaultHttpClientFactory
{
    public override HttpMessageHandler CreateMessageHandler()
    {
        var wasmHttpMessageHandlerType = Assembly.Load("WebAssembly.Net.Http").GetType("WebAssembly.Net.Http.HttpClient.WasmHttpMessageHandler");
        return (HttpMessageHandler)Activator.CreateInstance(wasmHttpMessageHandlerType);
    }
}

// In Startup, ConfigureService:
FlurlHttp.Configure(settings =>
{
    settings.HttpClientFactory = new HttpClientFactoryForBlazor();
});