Regression: Forms inside RTE-rendered Blocks do not re-render after POST in Umbraco 17 RC2 (works in RC1)

[kkarsin6]

Which Umbraco version are you using?

17 RC2

Bug summary

When a form is placed inside a Block (single block, not Block Grid) that is rendered inside an RTE, submitting the form in RC2 causes the block to render stale output.
The Razor view inside the block does not re-execute.

This results in:

@DateTime.Now not updating

ViewData values from the POST not appearing

The block output being reused from cache

This behavior worked correctly in RC1.

Specifics

No response

Steps to reproduce

Steps to Reproduce

1. Add a single block to an RTE.
2. In that block, render a form using a SurfaceController:

View inside block:

@model TestSearchViewModel

@using (Html.BeginUmbracoForm<ProductFinderFromController>(nameof(ProductFinderFromController.Submit)))
{
    <text>first load at: @DateTime.Now</text>
    <button type="submit">Hit me!</button>
}

@if (ViewData["CurrentTime"] is string t)
{
    <div>Submitted at: @t</div>
}

Controller:

[HttpPost]
public IActionResult Submit(TestSearchViewModel model)
{
    ViewData["CurrentTime"] = DateTime.Now.ToString("HH:mm:ss");
    return CurrentUmbracoPage();
}

3. Load the page → time renders correctly.

4. Click the button → POST executes.

5. Page re-renders, but the block output is frozen.

Expected result / actual result

Expected Behavior

• The Razor block should re-render after the POST.

• @DateTime.Now should show a new timestamp.

• ViewData["CurrentTime"] should show the submitted time.

• Block output should not be cached across form submissions.

Actual Behavior (RC2)

• The block inside the RTE does not re-render.

• @DateTime.Now remains the original value.

• ViewData["CurrentTime"] never appears or updates.

The block appears frozen or cached.

[github-actions]

Hi there @kkarsin6!

Firstly, a big thank you for raising this issue. Every piece of feedback we receive helps us to make Umbraco better.

We really appreciate your patience while we wait for our team to have a look at this but we wanted to let you know that we see this and share with you the plan for what comes next.

• We'll assess whether this issue relates to something that has already been fixed in a later version of the release that it has been raised for.
• If it's a bug, is it related to a release that we are actively supporting or is it related to a release that's in the end-of-life or security-only phase?
• We'll replicate the issue to ensure that the problem is as described.
• We'll decide whether the behavior is an issue or if the behavior is intended.

We wish we could work with everyone directly and assess your issue immediately but we're in the fortunate position of having lots of contributions to work with and only a few humans who are able to do it. We are making progress though and in the meantime, we will keep you in the loop and let you know when we have any questions.

Thanks, from your friendly Umbraco GitHub bot 🤖 🙂

[kjac]

Hi @kkarsin6

Thanks a lot for reporting this. We can reproduce - and this is a regression in RC2 for sure.

We'll look at a fix 👍

[kjac]

Test notes

This works in:

1. V13.latest.
2. V16.latest.
3. V17.RC1.

This is directly caused by #20681 re-introducing the Element level caching of property values.

The root cause is the cache rewrite not respecting Element level caching in the first place.

It is sufficient to simply render @DateTime.Now in the RTE block view. The first rendered output will remain until a re-publish of the page.

[kjac]

Fixed in #20880