问为什么在ImageSharp中不支持同步读取？

EN

- See this thread: [https://github.com/dotnet/aspnetcore/issues/7644](https://github.com/dotnet/aspnetcore/issues/7644)
- And this thread: [ASP.NET Core : Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead](https://stackoverflow.com/questions/47735133/asp-net-core-synchronous-operations-are-disallowed-call-writeasync-or-set-all)
- [This behaviour is controlled by `IHttpBodyControlFeature` - so you _can_ re-enable synchronous stream IO if you absolutely have to](https://stackoverflow.com/a/60985016/159145), but you really shouldn't.

// I assume this is a Controller Action method
// This method does not return an IActionResult because it writes directly to the response in the action method. See examples here: https://stackoverflow.com/questions/42771409/how-to-stream-with-asp-net-core

public async Task ResizeImageAsync( IBrowserFile file )
{
    await using( Stream stream = file.OpenReadStream() )
    using( Image image = await Image.LoadAsync( stream ) )
    {
        ResizeOptions ro = new ResizeOptions
        {
            Mode = ResizeMode.Min,
            Size = new Size(128)
        };

        image.Mutate( img => img.Resize( ro ) );

        if( file.ContentType == "image/png" ) // <-- You should not do this: *never trust* the client to be correct and truthful about uploaded files' types and contents. In this case it's just images so it's not that big a deal, but always verify independently server-side.
        {
            this.Response.ContentType = "image/png";
            await image.SaveAsPngAsync( this.Response.Body );
        }
        else
        {
            this.Response.ContentType = "image/jpeg";
            await image.SaveAsJpegAsync( this.Response.Body );
        }
}

public void ConfigureServices(IServiceCollection services)
{
    // If using Kestrel:
    services.Configure<KestrelServerOptions>(options =>
    {
        options.AllowSynchronousIO = true;
    });

    // If using IIS:
    services.Configure<IISServerOptions>(options =>
    {
        options.AllowSynchronousIO = true;
    });
}

using var image = await Image.LoadAsync(file.OpenReadStream());

public async Task<byte[]> ConvertFileToByteArrayAsync(IBrowserFile file)
{
    await using var image = await image.LoadAsync(file.OpenReadStream());
    image.Mutate(x => x.Resize(new ResizeOptions
    {
        Mode = ResizeMode.Min,
        Size = new Size(128)
    }));

    MemoryStream memoryStream = new MemoryStream();
    if (file.ContentType == "image/png")
    {

        await image.SaveAsPngAsync(memoryStream);
    }
    else
    {
        await image.SaveAsJpegAsync(memoryStream);
    }
    var byteFile = memoryStream.ToArray();
    memoryStream.Close();
    await memoryStream.DisposeAsync();

    return byteFile;
}