Render Output Invalid: Improve exception message

[jessicah]

aspnetcore/src/Components/Components/src/Rendering/RenderTreeBuilder.cs

Line 783 in eb18cb2

throw new InvalidOperationException($"Render output is invalid for component of type '{component.GetType().FullName}'. A frame of type '{invalidFrame.FrameType}' was left unclosed. Do not use try/catch inside rendering logic, because partial output cannot be undone.");

It took me an age to figure out my issue, as the exception wasn't the clearest as I had no try/catch behaviour. Can it also state that using break in a loop can also be a cause for this exception?

[mkArtakMSFT]

Thanks for bringing this up. Breaking mid rendering loop can be problematic (and cause and exception) if the rendered output is not "proper HTML". For example, if you're rendering table rows and break mid rendering, the closing tags for cell/row/table could end up not being rendered and the HTML structure would break.
So for these situations we recommend the customers to render proper closing tags for the context even after breaking.

We will see if we need to expand the exception message with a link to a documentation page, where we can expand more on this issue.