Kestrel options do not apply.

[Hergeirs]

Is there an existing issue for this?

• [X] I have searched the existing issues

Describe the bug

I'm using SkiaSharp for a project. They don't have an asynchronous API, so I need to set serverOptions.AllowSynchronousIO = true; in kestrel. For some reason it doesn't seem to have an effect. I'm only setting the option because I'm working with legacy code and can't really change the dependency on SkiaSharp at the moment. As soon as I run SKBitmap.Decode(stream); I get the exeption:

Unhandled exception. System.NotSupportedException: Synchronous reads are not supported.

I have been scouring every resource to try to find a solution.

Expected Behavior

Expect Asynchronous reads to work. After the setting is applied.

Steps To Reproduce

link for minimal git repo

Minimal steps to reproduce from template

• Create a new blazorserver project
  • dotnet new blazorserver -o BlazorApp -f net7.0
• Configure Kestrel by adding this line to program.cs directly beneath var builder = WebApplication.CreateBuilder();
  • builder.WebHost.UseKestrel().ConfigureKestrel(options => options.AllowSynchronousIO = true);
• Install SkiaSharp:
  • dotnet add package SkiaSharp.NativeAssets.Linux.NoDependencies
• Change contents of Pages/Index.razor to the following

  
  //  Pages/Index.razor
  @page "/"
  @using SkiaSharp
  @using Microsoft.AspNetCore.Components.Forms
  @using Microsoft.AspNetCore.Components

@code { private void OnChange(InputFileChangeEventArgs args) { foreach (var file in args.GetMultipleFiles()) { try { var stream = file.OpenReadStream(); var image = SKBitmap.Decode(stream); } catch (Exception) { // Ignore Invalid files } } } }

* Run ``` dotnet run ``` in a terminal.
*  upload a picture.
*  exception is thrown.

### Exceptions (if any)

Unhandled exception. System.NotSupportedException: Synchronous reads are not supported.
   at Microsoft.AspNetCore.Components.Forms.BrowserFileStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at SkiaSharp.SKManagedStream.OnReadManagedStream(IntPtr buffer, IntPtr size)
   at SkiaSharp.SKManagedStream.OnRead(IntPtr buffer, IntPtr size)
   at SkiaSharp.SKAbstractManagedStream.ReadInternal(IntPtr s, Void* context, Void* buffer, IntPtr size)

### .NET Version

7.0.403

### Anything else?

Editor: ```NVIM v0.9.4```

## dotnet --info

.NET SDK: Version: 7.0.403 Commit: 142776d834

Runtime Environment: OS Name: arch OS Version: OS Platform: Linux RID: arch-x64 Base Path: /usr/share/dotnet/sdk/7.0.403/

Host: Version: 7.0.13 Architecture: x64 Commit: 3f73a2f186

.NET SDKs installed: 7.0.403 [/usr/share/dotnet/sdk]

.NET runtimes installed: Microsoft.AspNetCore.App 7.0.13 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.NETCore.App 7.0.13 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found: None

Environment variables: DOTNET_ROOT [/usr/share/dotnet]

global.json file: Not found

Learn more: https://aka.ms/dotnet/info

Download .NET: https://aka.ms/dotnet/download

[BrennanConroy]

Blazor is throwing that error directly. It has nothing to do with Kestrel. https://github.com/dotnet/aspnetcore/blob/c15938bb5f23fd3ad2374bde554a6b492a36ecde/src/Components/Web/src/Forms/InputFile/BrowserFileStream.cs#L56

[Hergeirs]

I figured. Just tried the only option looking mildly applicable in the docs.

Is there an option to configure Blazor itself to allow it then ? Or at least a workaround without changing the dependency?

[SteveSandersonMS]

The BrowserFileStream can't support synchronous reads because it's reading from a file in the browser's memory, which is only reachable over the network (in the Blazor Server or WebView case).

As a solution in your case, can you asynchronously read the file into memory (as a byte[]) before passing that data to SKBitmap.Decode?

[ghost]

Hi @Hergeirs. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[Hergeirs]

Thank you @SteveSandersonMS I should have thought of that. It worked flawlessly.

So basically just changed it (in this example) to:

                using var stream = file.OpenReadStream();
                using var memStream = new MemoryStream();
                await stream.CopyToAsync(memStream);
                var image = SKBitmap.Decode(memStream.ToArray());

[SteveSandersonMS]

Yes that's correct.