Add async operation for ToHtml() method

New Feature Proposal

Description

Add async operation for Node.ToHtml(TextWriter writer, IMarkupFormatter formatter) method.

Background

In AspNet Core 3.0, Synchronous IO is disallowed in default, AllowSynchronousIO disabled in all servers, this means if we call doc.ToHtml() in AspNet will throw an error: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.

AspNet code:

using (var writer = _writerFactory.CreateWriter(Response.Body, encoding){
    doc.ToHtml(writer);
    await writer.FlushAsync();
}

Specification

Wish to add new ToHtmlAsync() method for asynchronous IO operation or add new options for ToHtml() allows asynchronous write operation.

[Tratcher]

@zhengchun what’s the stack trace for the exception?

Writing to a MemoryStream should be fine, but flushing it out to the response body needs to be async.

[FlorianRappl]

Hi @Tratcher that’s certainly a good point. The average write here is about 4 to 16 characters dep. on the document. So we do not talk in ~1k (or more) chunks (which would benefit the specific IO). With small I refer to a single write unit in AngleSharp - which is way less than usual IO buffers used these days.