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, or a RenderFragment placed as content, reports BCF3003.

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 (BCF3008) and cannot be a ForEach content root (BCF3003).

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.Class("prose")[Raw(entry.Html)]

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.