Control Flow

Conditionals and lists are expressed with dedicated constructs so the generator can assign compile-time sequence numbers to every position in the template.

If#

If takes a condition and a content thunk, with an optional else branch:

protected override View Body =>
    Div(
        If(_items.Count == 0,
            () => P("Nothing here yet."),
            () => Span($"{_items.Count} items")));

Mutually exclusive branches get disjoint sequence ranges, so switching branches never disturbs the sibling positions around them.

Keyed ForEach#

ForEach requires a key that identifies the item, not its position:

protected override View Body =>
    Ul(
        ForEach(_items,
            key: item => item.Id,
            content: item => Li(item.Name)));

Sequence numbers identify template positions; keys identify data instances. Passing an index as the key defeats the diff — reordering the list would make Blazor reuse the wrong element state. The content root must be a single element or component, so a Fragment or Raw root reports BC3003.

Fragment#

Fragment groups children without emitting a wrapper element, the equivalent of <>...</>:

Fragment(H2("Title"), P("Body"))

Because it opens no element it cannot be decorated (BC3008) and cannot be a ForEach content root (BC3003).

Raw#

Raw injects a trusted HTML string verbatim, the MarkupString equivalent. This page itself is rendered that way — its Markdown is converted to HTML at build time and passed to Raw.

Article(Raw(entry.Html)).Class("prose")

Raw writes to the DOM without escaping, so it accepts trusted content only. Never flow user input or an external response through it.

Next#

See elements and decorations for the element vocabulary.