support-prerendering

Blazor prerendering runs OnInitializedAsync twice, causing duplicate data loads. Annotate the property with [PersistentState] and use the ??= pattern so data fetched during prerender is serialized and restored when the interactive runtime attaches instead of being re-fetched.

Disable prerendering by setting prerender: false on the render mode, for example @(new InteractiveServerRenderMode(prerender: false)) on a component, instance, or the HeadOutlet and Routes in App.razor. A parent's setting overrides children, so disabling on Routes affects all pages.

OnAfterRenderAsync is not called during prerender because prerendering produces static HTML with no browser runtime attached. It only fires after the interactive Server or WebAssembly runtime loads, so JS interop calls must be placed there rather than in OnInitializedAsync.

HttpContext is only available during the static prerender phase, not during the interactive lifetime of a component. For pages needing cookies, headers, or response status codes, apply [ExcludeFromInteractiveRouting] so the page renders via static SSR with full HttpContext access.

Components in the .Client project prerender on the server, so services registered only in the client Program.cs are unavailable. Fix this by registering a matching server-side service, making the dependency optional, creating a shared abstraction, or disabling prerendering for that component.