Rendering huge HTML report using HtmlRenderer outside of ASP.NET Core

[grsw92]

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Hi,

Following this documentation: https://learn.microsoft.com/en-us/aspnet/core/blazor/components/render-components-outside-of-aspnetcore?view=aspnetcore-9.0 I created a sample app that is able to generate emails and it works flawlessly out of the box (big kudos for that 👍).

However, the second scenario I would like to employ this mechanism to is to generate html-based reports with possibly thousands of records (perhaps even more). I set up such code based on the sample from article above and instead using .ToHtmlString() used .WriteHtmlTo(TextWriter) to write the report directly to the file. Unfortunately, from my testing it appears it does not matter what writer is used the memory allocation made by the renderer itself is significant. It seems that the HTML is not rendered on the fly directly to the stream, instead the whole thing is built and stored into memory and when it's ready then it's serialized into HTML string. Can you confirm this is what really happens?

If that's the case, have you considered supporting this kind of scenarios in the future? Do you have any recommendation how could I approach this problem with using the current implementation?

Describe the solution you'd like

The HTML report rendered directly to the stream as it flows without allocating the whole view in memory.

Additional context

No response

[javiercn]

@grsw92 thanks for contacting us.

This is by design. Blazor builds and in-memory representation of the DOM (similar to how other frameworks like React do) and doesn't support "streaming" in the sense that you are looking for.

This is not going to change as it is fundamental to the Blazor model and programming experience associated with it. If you have thousands of records, you could instead render a header, put a placeholder in, and then render each record individually, which should allow you to "stream" the response into that placeholder.

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