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Event Bindings

AXSG supports event bindings as compile-time features instead of treating event hookup as a purely runtime, string-based concern.

Supported forms

Handler-name binding

Use a CLR method name when you want a stable named handler on the root or typed source context:

<Button Click="OnSaveClicked" />
<Button Click="{Binding SaveClicked}" />

This mode is useful when the handler already exists as a method and should participate in normal symbol navigation.

Inline lambda form

Use an inline lambda when the behavior is short and local to the XAML site:

<Button Content="{$'{ClickCount} clicks'}"
        Click="{(sender, e) => ClickCount++}" />

Inline statement-block form

Use CSharp when the event logic is multi-line or needs local sequencing:

<Button.Click>
  <CSharp><![CDATA[
source.ClickCount++;
source.LastAction = $"Clicked by {sender}";
  ]]></CSharp>
</Button.Click>

Semantic rules

  • Event handlers are resolved against the event delegate type.
  • Inline lambdas are compiled against the real event signature.
  • AXSG rejects async lambdas in the current event-binding surface.
  • Generated handler methods use stable identities so hot reload and Edit-and-Continue remain deterministic.

Tooling support

The language service understands event bindings for:

  • completion of handler names and lambda bodies
  • hover over event parameters and referenced members
  • go to definition and find references for event methods, properties, and context variables
  • semantic highlighting and inline C# projections in the VS Code extension