Section

Section is a heading and the controls it heads.

It draws the title and nothing else — no border, no background. A settings window is a column of sections, and one that framed every section would read as a stack of cards; what says where one section ends is the next one's heading. The theme gives it a column, a heading with some weight, and a column for the content.

The landmark half of doc 49 § 7.1's fourth rank. GroupBox says *these controls answer one question*; Form says these fields are sent together; Section says *this is a part of the page, and here is its name*. It is HTML's <section aria-labelledby> with its <h2>.

• ⚠ Two nodes in the accessibility tree, on purpose. A screen-reader user moves through a long page by landmark and by heading, and a section has to be reachable both ways. So the heading is a real AccessibleRole.Heading node, and the section is an AccessibleRole.Region named by it through LabelledBy — ARIA's own pattern. The title is one property and one copy: the words on screen are the words both nodes announce.

``text region "Audio" heading "Audio" slider "Volume" = "0.5" ``

• ⚠ Unnamed, it is still a region, and the tree says so. ARIA exposes a <section> with no name as a plain generic, and a control that did the same would hide the omission. Section keeps its role, and AccessibilitySnapshot.Unnamed reports an unnamed region — the one landmark ARIA requires a name of. A section that should be a landmark without a visible heading sets AccessibleName, which wins over the heading.
• No title, no heading. The heading part is hidden when there is no title, and its role goes with it — the accessibility tree walks hidden parts, so an empty heading left as one would be announced as a heading with no name.

Nest controls in markup, and they land in Content. From C#, section.Add<T>() and section.Content.Add<T>() are the same call: Add parents on the control's content host, which is where a nested tag goes (#1425). Writing Content says so at the call site:

Title is what the heading says and the section's name. Heading is the part it is drawn in, for a theme or a test.

Limits.

• ⚠ No heading level. The accessibility model has no aria-level, so a section inside a section is announced as a heading exactly like its parent's. The theme draws every section heading at one size.
• It does not collapse. That is Expander (see Markup panels), whose header is a button saying what it opens.
• It is not a form. Put a Form inside a section, or sections inside a form, as the page needs — the two answer different questions and compose.

A settings page. Each section a landmark, each heading a stop for heading navigation, each row a named field:

A heavier heading. The heading is its own tag:

• Group box — the bordered box round controls that answer one question.
• Form — what submits the fields in a section, and refuses while one is wrong.
• Labeled content — the row that names one field.
• Accessibility — roles, names, landmarks and the gates that hold them.